does it work when you enter about:config into the firefox address bar (confirm the info message in case it shows up) & revert all custom set preferences (=shown in bold) starting with network or security to their default state? right-click such entries in order to reset them...

No problem here, so this is a problem on your computer.

Try to rename the cert8.db file (cert8.db.old) and delete the cert_override.txt file in the Firefox profile folder to remove intermediate certificates and exceptions that Firefox has stored.

If that has helped to solve the problem then you can remove the renamed cert8.db.old file. Otherwise you can rename (or copy) the cert8.db.old file to cert8.db to restore the previously stored intermediate certificates. Firefox will automatically store intermediate certificates when you visit websites that send such a certificate.

If that didn't help then remove or rename secmod.db (secmod.db.old) as well.

You can use this button to go to the current Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/

Create a new profile as a test to check if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

kushagra said

does it work when you enter about:config into the firefox address bar (confirm the info message in case it shows up) & revert all custom set preferences (=shown in bold) starting with network or security to their default state? right-click such entries in order to reset them...

No. I've been through all of the suggested fixes I could find on these forums and nothing works. It seems that the root of the problem is that https://accounts.firefox.com/ will not return a valid certificate (or at least not one the v 39 recognizes).

cor-el said

No problem here, so this is a problem on your computer. Try to rename the cert8.db file (cert8.db.old) and delete the cert_override.txt file in the Firefox profile folder to remove intermediate certificates and exceptions that Firefox has stored. If that has helped to solve the problem then you can remove the renamed cert8.db.old file. Otherwise you can rename (or copy) the cert8.db.old file to cert8.db to restore the previously stored intermediate certificates. Firefox will automatically store intermediate certificates when you visit websites that send such a certificate.

As I indicated in my original post No. I've been through all of the suggested fixes I could find on these forums, including the ones you recommend, and nothing works. It seems that the root of the problem is that https://accounts.firefox.com/ will not return a valid certificate (or at least not one the v 39 recognizes). Hard o see how that's a problem with my computer.

If I have to go through this kind of computer forensic analysis every time I add a computer that needs to sync with FireFox , then the sync (non) functionality ceases to be a time saver. From the number of posts I've seen on this subject in this forum and on Google and on Bing, this is not an isolated problem.

I just wonder how many people have had this problem, got frustrated and just decided to move on to another browser.