Can you bring up the Profile Manager to create a new profile? Try to create a new profile as a test to check if your current profile is causing the problems. 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 some files from an existing profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over the problem. *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox