Create a new profile as a test to check if your current profile is causing the problems. <br> See '''Creating a profile''': *https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles *http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over the problem <br> '''Profile Backup and Restore''' *http://kb.mozillazine.org/Profile_backup *https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Thank you! I still don't know exactly what broke, but I have a new profile with the old files, bookmarks and tabs etc from a backup. Up and running! Thanks — David