What happens if you try to clear the recent history and which items have a check-mark and what is the range? *https://support.mozilla.org/kb/Clear+Recent+History Note that clearing "Site Preferences" clears all exceptions for cookies, images, pop-up windows, software installation, and passwords. Clearing cookies will remove all specified (selected) cookies including cookies with an allow exception that you would like to keep. ----- 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