Firefox may have refreshed and has crated a new default profile. Do you have an "Old Firefox Data" folder on the desktop that could have your old profile data? It is possible that there has been a problem with the profiles.ini file that registers profiles and that a new default profile got created. You can check if you have orphaned profiles that aren't registered in profiles.ini and that do not show in the Profile Manager. You can check that by opening the current profile folder and go up one level. *http://kb.mozillazine.org/profiles.ini_file *~/Library/Application Support/Firefox/Profiles/&lt;profile&gt;/ In Mac OS X v10.7 and later, the ~/Library folder is a hidden folder. *http://kb.mozillazine.org/Show_hidden_files_and_folders#Mac_OS_X You can recover an orphaned profile that is no longer registered in the Profile Manager via these steps: *use the Profile Manager to create a new profile *click "Choose Folder" in the Profile Manager *browse to the location of a lost profile to recover this profile and register it in the Profile Manager Note that you should never use "Choose Folder" to specify a folder that already contains files that do not belong to Firefox (i.e. only use "Choose Folder" to recover an orphaned profile) ---- You can also check for problems with the <b>places.sqlite</b> database (bookmarks and history) in the Firefox profile folder. *https://addons.mozilla.org/firefox/addon/places-maintenance/ See also: *http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox *https://support.mozilla.org/en-US/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file If the Places Maintenance extension 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 about:profiles page. *Help -> Troubleshooting Information -> Profile Directory: Show in Finder *http://kb.mozillazine.org/Profile_folder_-_Firefox