see -- http://kb.mozillazine.org/Kill_application which explains how to completely exit (quit) your Mozilla application Try closing Firefox completely *Close Firefox properly '''File > Exit''', not with the "X" which just closes the window. *Use the Windows Task Manager "Processes" tab to make sure that firefox.exe is not running and also that the plugin-container.exe is not running. If that does not work, try restarting the system. If still no luck try restoring bookmarks from last backup, or better create your own .json backup and restore from that. *http://kb.mozillazine.org/Backing_up_and_restoring_bookmarks_-_Firefox#Creating_bookmark_backups *''If you had to go this far, please provide feedback if restoring bookmarks alone fixed the problem. I think I may have done that once with success, but never see that suggested -- I'd try most anything to not lose history or bookmarks. But then I could restore files from my profile and restore latest bookmarks backup from current profile.'' The following will result in complete loss of history if it comes down to deleting places.sqlite, so rename files rather than deleting. With Firefox down. Of course you have backups of your profile you could replace rename and replace those files instead. Locked or damaged places.sqlite - MozillaZine Knowledge Base :"Toolbar buttons such as Back/Forward are disabled " :http://kb.mozillazine.org/Locked_or_damaged_places.sqlite