You can check for problems with the <b>places.sqlite</b> database (bookmarks and history) in the Firefox profile folder. *use "Verify Integrity" on the "Help -> Troubleshooting Information" (about:support) page *https://addons.mozilla.org/firefox/addon/places-maintenance/ See also: *http://kb.mozillazine.org/Locked_or_damaged_places.sqlite *https://support.mozilla.org/en-US/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file If "Verify Integrity" on the "Help -> Troubleshooting Information" (about:support) page or Places Maintenance can't repair the places.sqlite database then remove all places.sqlite file(s) in the Firefox profile folder to make Firefox rebuild the places.sqlite database from the most recent JSON backup in the bookmarkbackups folder. *keep a backup copy of places.sqlite in case a new places.sqlite database has to be created *http://kb.mozillazine.org/Unable_to_process_the_backup_file_-_Firefox You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the <b>about:profiles</b> page. *Help -> Troubleshooting Information -> Profile Directory:<br>Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder *http://kb.mozillazine.org/Profile_folder_-_Firefox