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Firefox Portable unusable: How to Fix the “Firefox Is Already Running” Error

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xprt007
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Firefox Portable unusable: How to Fix the “Firefox Is Already Running” Error

Hi there

I have a very annoying problem with Firefox Portable. I have the latest available version as of today, Windows 10 Home 64 bit, 8GB RAM notebook, all Windows updates installed.

Because I had many tabs + 2, 3 windows open when I started the notebook from hibernation, it was taking a bit long for it to completely "wake up", so I decided to close Firefox, which I assume was taking most memory via Taskmanager, something I have done countless times before, on this notebook.
Usually you see "Mozilla Firefox, Portable edition..." under "Apps" & "Background processes" in the Taskmanager. I was in a hurry and started with closing the Firefox instance I saw under Background processes, before going to quickly close the instances under Apps.

I have never ever had a problem with closing Firefox or any process before via the task manager.

When I tried to start Firefox shortly after that, I got the error message another instance was running & I should first close it, although there was clearly none visible in the Task manager, that I should first close!
I also tried another instance of Firefox portable I have at another location, same problem.

I re-started the notebook and to my surprise, I now get the error message whenever I try to start Firefox portable like I have done thousands of times before, although no one has started any instance before. This is very frustrating, since it has my bookmarks & other settings but cannot use it and no other instance or Portable firefox installed elsewhere is usable!!.

How can I urgently resolve this?

UPDATE:
I have a a separate version of Firefox installed from mozilla.com, ie. not the portable version mentioned above, which I rarely use. Originally, after noticing the above problem, I tried it out & it worked BUT right now, it is also showing the same error when I try to start, although as said there is no indication in the task manager that any instance of firefox is running. I am using this Firefox version for the first time today, since I normally use the portable version, but out of the blue, it is also suddenly not starting. What coould be triggering a problem I have never heard, except years ago, when I had a similar problem, but at least then, one could see an instance in the Task manager, that was for some reason not closing when one closed Firefox? At that time, I think there was a fault solved subsequently by an update.

So now I have 2 problems, with a fresh version of Firefox installed from this site but never used, except today + Firefox Portable, both currently unusable.

Was the problem closing the instance under "Background processes" before that under "Apps" in task manager which caused some corruption (of what/where??), although as I have said, I have over these many years never had any issue with closing any program whatever the order in task manager.
How could that have affected the Firefox installed from this site but never used except today, because i certainly did not close it in any unusual way????

I did find out from Mozilla.com forums, one could delete parent.loc in C:\Users\user\AppData\Roaming\Mozilla\Firefox\Profiles\cgv2ibk9.default-release and that seems to help the installable Firefox start normally with the file apparently recreated BUT trying to delete the similar file I saw in the portable version at D:\Portableapps\FirefoxPortable\Data\profile makes no difference.
The question is what triggers this to affect not only this, but another portable version in another location + the installable version from Mozilla, when I have never had a similar issue in over 15 years of use?

Thank for your quick response.

John T. Haller
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Exact Error

Please post the exact error verbatim and whether it is Firefox yielding the error or the Firefox Portable launcher. The title of the error window should be a clue.

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xprt007
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Thank you for the quick

Thank you for the quick response.
The exact error message is:

At the top of the popup-window, we have Mozilla Firefox, Portable Edition | PortableApps.com
Message:
"Another instance of Firefox is already running. Please close other instances of Firefox before launching Mozilla Firefox, Portable Edition."

As said, this error message pops up after trying to launch my preferred version of Firefox, ie the Portable Edition, even after restarting the PC, with no Firefox launched, as soon as I try to launch the Portable version at the above location D:\Portableapps\FirefoxPortable\ or on another partition, although before today's mentioned incident above, this has never happened before in that form, as even in Task Manager, there's clearly no form of firefox running. So for the last couple of hours, after forcibly closing it via Task manager, it has not been possible to successfully launch the portable edition. Again as mentioned, deleting "parent.lock" at D:\Portableapps\FirefoxPortable\Data\profile, does not help, whereas following one of the options in the instructions in Mozilla.com forum to solve an issue throwing a similar error at C:\Users\user\AppData\Roaming\Mozilla\Firefox\Profiles\cgv2ibk9.default-release, made the non-portable version work.

I had made no changes to anything on the notebook and was just launching Firefox as I always do this morning ...

I hope this helps identify the problem.

Kind regards

John T. Haller
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firefox.exe

This should only occur if firefox.exe is running somewhere on the system either under your user account or another one. Do you have multiple user accounts setup on this PC? Did you do a full reboot?

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xprt007
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I have only one user account

I have only one user account on this notrebook which I use, after recently installing Windows 10.

After reading your comment, I did shut down the notebook, but on power up, went straight to Firefox Portable and got the same message. Same from a separate and hardly used instance of same program in a separate location.

Although I am quite sure I have no other instance of Firefox running somewhere, I uninstalled the version from Mozilla.com, which I had never used since I installed it, the day I installed Windows 10, except yesterday, when this issue started.
I shutdown the PC again, booted up, same problem with Portable Firefox, both instances.

This is simply crazy.
I installed a new copy of Firefox Setup 87.0.exe and after unexpectedly getting a message: "your firefox profile cannot be loaded. it may be missing or inaccessible", I went to AppData and deleted the Firefox folder, and it started successfully. No complaint about some hidden instance of Firefox.exe running somewhere.

To sum this up, I mostly use Hibernation when stepping away from notebook, so I can immediately access the usually many, mostly open Firefox tabs
as I often use the notebook offline. With this particular notebook, because it can be a bit slow to fully "wake up", so I can access the tabs, sometimes I instead just end Firefox using the Task Manager as it may be faster. I have done that a thousand times with no issue.
Yesterday, I decided to do the same, starting with closing the task of Firefox I saw under "Background apps", before closing those above under "Apps" in task manager. That is something I just noted.
As soon as I went to start Firefox again/afresh, I suddenly get this message and crosscheck only to see no related task still running in Task manager. It sounded like a joke at first, but then I noticed I could not start Firefox at all, not even an unused instance in another location.

I have used Firefox longer than when I signed up on this site in 2008 and have probably installed hundreds of instances on different media & gadgets and I have never had it fail to start, especially with this error message. Where that error message has appeared, you could see the instance running in task manager and close, then it starts with no problem, but this time, there is none.

Does Firefox Portable store some files somewhere in Windows which might have been corrupted during the forced ending of the task in task manager and if so where is it so whatever it is can be deleted as it seems to be preventing ALL instances of Firefox Portable from running including a fresh instance of FirefoxPortable_87.0_English.paf.exe I have just installed as I am writing this, saving it at yet a different location and it also gives this crazy message?

I copied the second copy of Firefox Portable mentioned above, ie installed outside luancher to a USB flash drive, transported it to another old notebook, where it starts with no issue, meaning its files are note courrupted and whatever the problem is, it must be on the this notebook, but what is it, interferring with Firefox Portable?.

Thank you for your time and help.

Kind regards

.

John T. Haller
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Shouldn't

There shouldn't be anything left behind and the launcher should only show that message when the Windows API says that firefox.exe is running somewhere. Let's try to attack this a piece at a time.

First, check both your C drive and, if different, the drive Firefox Portable is running on for errors. You can right-click on them in Explorer, select Properties, select the Tool tab and select to scan it for errors.

Second, reboot your PC for good measure and don't start up any apps.

Third, uninstall your local copy of Firefox as long as you don't need it. Do this in the Control Panel. After it's uninstalled, browse to both C:\Program Files and C:\Program Files (x86) and delete the Mozilla Firefox directories within there. Then delete C:\Users\USERNAME\AppData\Roaming\Mozilla\Firefox and C:\Users\USERNAME\AppData\Local\Mozilla\Firefox.

Fourth, run Disk Cleanup. Click Start and start typing cleanup, then select Disk Cleanup. Select C: and click OK. In the new window, click Clean up system files. Select everything and click OK. Note that this will mean you can't go back to an earlier build of Windows 10. If you think you may need to, you can uncheck that option.

Fifth, download a fresh copy of Firefox Portable from our site and install it to your Desktop directory temporarily. Try running FirefoxPortable.exe within there and let me know if that works. If it does, close it and delete it, then try your existing Firefox Portable install.

Sometimes, the impossible can become possible, if you're awesome!

xprt007
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That seems to solve the problem

Hi there

I went through the instructions above, with no errors found on both partitions C & D, (Portable Firefox on D). I deleted the folders, with Mozilla Maintenance or something like that also in addition.

The fresh Firefox worked, as well as the usual one in the launcher & the other instances.

Could it be the rogue files preventing the launch of Portable Firefox, probably deleted during Disk Cleanup were created because the normally harmless ending of the Firefox process via Task manager probably occurred at some unfortunate moment, interrupting the shutdown and corrupting some files when the instance under "Underground apps" was done?

Many thanks for your assistance.

tyee
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I'm getting something similar

I'm getting something similar. I think I did something last night during getting zoom to work with my camera. It finally worked and I thought all was good. I normally run Firefox Portable in Sandboxie and it still runs there fine. This is the strange part - If I try to run it outside of the sandbox I get the same error about Firefox already running. Anything come to mind that could cause that? If I delete the parent.lock file, it does run but I get another error about Places and Favicons databases can't be read (according to Mozilla). So I'm wondering why it works in the sandbox and does not work outside it. Something must not be copied into the sandbox which allows it to work. I will try the above steps and see what happens. Also, another thing I noticed, in "about:profiles" I see my older profiles from the installed version from many years ago and the places and favicons database files have current date stamps. I thought Firefox Portable only used the portable Profile folder and not anything else on my PC?

tyee
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Well, I uninstalled my old

Well, I uninstalled my old version, deleted all the mentioned files and installed ver. 87 again into a brand new folder and it ran fine. I then tried to run my current version and I get this - "(Error code: sec_error_library_failure)". Mozilla says to run "Refresh Firefox", but I don't see that button on the portable version in the troubleshooting page?

Oh, yes, I remember why this started happening. In the last few days with ver. 87, it hangs randomly on me. So I have to close the window and restart. It has always restarted in the sandbox just fine, but now not out of the sandbox. My old version, ver. sixty something never hung.

Update - OK, I'm getting somewhere. As said the new install of ver 87 starts fine. I copied my current places.sqlite file into the new install profile folder and guess what. I got the same error...which means...not sure, is places.sqlite corrupt? To find out I ran my current portable version in the sandbox again and it started fine like I said before. I then compared byte by byte it's places.sqlite with the version that won't run on the new install. Result is they are identical. This is really playing with my mind. Let me try to summarize -

Error decribed below = The bookmarks and history system will not be functional because one of Firefox's files is in use by another application.

Current portable install runs fine in Sandboxie
Current portable install gives error outside of Sandboxie
New portable install runs fine outside of Sandboxie
New portable install gives same error if places.sqlite is copied from current install
This current install places.sqlite is byte identical to places.sqlite run in Sandoxie

hdmi
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similar problem

Firefox Portable 88.0 (64-bit) and FirefoxPortable.ini with the line AllowMultipleInstances=true are both located in my C:\FirefoxPortable folder. When I run C:\FirefoxPortable\FirefoxPortable.exe everything works fine until I run it again before I close it, as doing that gives an error dialog window: "Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window."

As for using it with Sandboxie, yes, I am able to run one instance of Firefox Portable sandboxed, one instance of Firefox Portable non sandboxed. But if I try to run more than one instance sandboxed or more than one instance non sandboxed, then no. Tested on two different laptops both running in Windows 10 Home x64 version 20H2 build 964. Fix, please... tanks! Smile

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