I had this problem yesterday right after the 3.6.4 upgrade. Im not sure if I saw all the things you did but I def lost all bookmarks and the back button. I have fixed it by: 1. Going to the Firefox profile directory which for me is here but 1st bit will be different for you as mines work specific: C:\Documents and Settings\U049177\Application Data\Mozilla\Firefox\Profiles\soez0lvk.default 2. Delete places.sqlite and places.sqlite-journal 3. Start Firefox (you should have the back button working now but no bookmarks, it will have recreated those 2 files) 4. From the menus, Bookmarks then Organise Bookmarks, then Import and Backup button, then Restore then select a day to restore from. You should now have your bookmarks back from Firefoxes backups. Hope it works for you