This may be a problem with my environment, but I thought I'd throw it out there anyway.
I've started getting the follwing message screens on several sites - Dropbox and Google+ to name two.
Your connection is not secure
The owner of www.dropbox.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.
This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox may only connect to it securely. As a result, it is not possible to add an exception for this certificate.
Any idea where to begin looking? I've got regular Firefox 49.0.2 installed in other virtual machines and they work just fine.
Thanks in advance.
I cant duplicate the problem, with either of those sites.
I would recommend a) running a virus scan on your machine, and b) ensuring nothing has changed with your access point (router, etc) that could be causing the errors at that point.
This is nearly always due to an antivirus or software firewall product inserting itself into the HTTPS connection but not properly configuring itself to adjust Firefox Portable's settings (it will normally only adjust a local Firefox's settings to decrease security and let it intercept and analyze HTTPS traffic). You'll need to manually configure Firefox Portable and other portable browsers to work with these traffic interception/analysis products or turn them off.
Sometimes, the impossible can become possible, if you're awesome!
Anti-Virus (McAfee) runs full time and if anything was there, the powers that be would let me know about it short order. And they have the configuration locked down tight to where I can't change anything.
Once again access points, routers, etc are out of my control.
How would I go about manually configuring Firefox Portable?
University policies prevent me from changing very many things at all. Windows group policies are set and then locked down..
It sounds like you are behind a firewall and/or proxy. You need the proper root certificate file imported into Firefox. You would need to get that from the University tech support. This is NOT a problem with Portable FF.
Go to Tools > Options > Advanced
Click on the Certificates tab
Click View Certificates (Opens Certificate Manager)
Click on the Authorities tab
Browse to the root certificate
Found the problem.
the cert8.db file had been corrupted somehow. it was only about 1K.
Fortunately I had the Firefox 2nd Profile installed and copied the cert8.db (112k) from that.
Voila, problem is gone.