It is possible that there is a problem with the files sessionstore.js and sessionstore.bak in the Firefox Profile Folder.

Delete the files sessionstore.js and sessionstore.bak in the Firefox Profile Folder.

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder
• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/sessionstore.js

If you see files sessionstore-##.js with a number in the left part of the name like sessionstore-1.js then delete those as well.
Deleting sessionstore.js will cause App Tabs and Tab Groups and all open tabs to get lost, so you will have to create them again (make a note or bookmark them).

See:

• http://kb.mozillazine.org/Session_Restore

Thank you very much, problem solved!! Headaches gone!! :)

You're welcome

Deleting the sessionstore files didn't work for me for very long--soon they started accumulating again. But what did work was starting up Firefox in safe mode, then closing it. Next time I started Firefox: eureka, problem solved.

Yes mine also started again a few days later and I had to delete the files again. If it happens again I will try your solution.

I have another problem that happens occasionally though, normally when I click on one of my favourites it opens in a new tab but from time to time it opens in the tab currently selected and that is frustrating as it means the site I was on is gone.

Any ideas?

If you have problems with files in the Firefox Profile Folder then make sure that cleanup software (e.g. CCleaner) or other security software isn't messing with those files or protecting them otherwise because of the .js file extension.

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