Firefox 16.01 Portable, tabs cannot close. I can close the window of course. The X on the tab doesn't work. Right clicking and choosing Close Tab doesn't work. Right clicking another tab and choosing Close Other Tabs doesn't work.
Firefox 17 Beta Portable, JavaScript errors out the wazoo. Mostly on Facebook. YouTube as well.
Firefox 16.01 doesn't have the tab issue at home, and I generally use the same extensions on both home and portable. Portable doesn't have the Reddit extension and a couple home-specific extensions. Tab Mix Plus is on both but again, tabs close on installed 16.01.
Probably specific to an extension or something, just wanted to throw it out there and see if anyone else had the issue.
/edit: I thought y'all said the word verification was only on iffy posts. I'm starting to take this personally, LOL. 
Visit the Community page
Join our forums
Subscribe to our email newsletter
Subscribe with RSS
Follow us on Facebook
Follow us on LinkedIn
Follow us on Twitter
Follow us on Mastodon
Follow us on BlueSky
You can simply find out, whether your Add-ons are the cause for the problem in your portable Firefox browser. Please click on your orange Firefox button at the top left, then click on Help->Restart with Add-ons Disabled...
Didn't really help (but thanks anyway) because in Safe Mode I couldn't enable extensions one at a time to see which one breaks it. So I restarted, and started disabling extensions and restarting.
As I suspected, it was Tab Mix Plus. However, TMP doesn't break tab closing in the installed Firefox 16.01, so the tab thing is still a mystery. I will have to verify the versions are the same (0.4.0.3 on the portable) but the portable version can't update, so I assume it's on the latest. That means if the home version is a version out, updating it will (probably) break it.
That sucks, I really like TMP. TMP probably won't fix it if the problem only exists in the PortableApps.com edition. Or if it's a specific conflict between Firefox 16 + TMP + Some Other Extension. Ugh. But thanks.
Not gonna track down Beta 17's problem just yet.
Beta 17 probably introduces a change that breaks Tab Mix Plus. I doubt the author won't fix it before 17 is official.
Basically my advice regarding the usage of the safe mode only should help you to find out, whether an extension in Firefox is the cause of your problem. If the problem does not occur in safe mode, please try to isolate it down to an individual plug-in. Here now the following instructions as must be done:
As you already have mentioned, your extension "Tab Mix Plus" seems to be the cause. However you should examine with the above method, if any further extensions lead to a conflict.