If you have submitted crash reports then please post the IDs of one or more recent crash reports that start with "bp-": *bp-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx You can find the report ID of recent crash reports on the "Help > Troubleshooting Information" page (about:support). *click the "All Crash Reports" button on this page to open the <b>about:crashes</b> page and see all crash reports. Alternatively you can open about:crashes via the location/address bar. See also: *http://kb.mozillazine.org/Mozilla_Crash_Reporter *https://support.mozilla.org/kb/Mozilla+Crash+Reporter ----- Your System Detail list shows that you have a user.js file in the profile folder to initialize prefs each time Firefox starts. The user.js file will only be present if you or other software has created this file and normally won't be present. You can check its content with a plain text editor (right-click: "Open with"; do not double-click). The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session. You can delete the user.js file if you didn't create this file yourself. You can use this button to go to the current Firefox profile folder: *Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder) *http://kb.mozillazine.org/Profile_folder_-_Firefox *http://kb.mozillazine.org/Preferences_not_saved