It is possible that there is a problem with the files [http://kb.mozillazine.org/sessionstore.js sessionstore.js] and sessionstore.bak in the [http://kb.mozillazine.org/Profile_folder_-_Firefox Profile Folder] Delete [http://kb.mozillazine.org/sessionstore.js sessionstore.js] and sessionstore.bak in the [http://kb.mozillazine.org/Profile_folder_-_Firefox Profile Folder] * Help > Troubleshooting Information > Profile Directory: Open Containing Folder 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 to get lost, so you will have to create them again (make a note). See: * http://kb.mozillazine.org/Session_Restore

Didn't work. The tabs still reopens. Thanks anyways...

Is Firefox creating a final file sessionstore.js that doesn't have a "session":{"state":"running"} at the end of the file ? See "Hang at exit": * http://kb.mozillazine.org/Firefox_hangs * [[Firefox hangs]]

Never mind. Reverted to Firefox 3.6. Problem fixed...