See https://support.mozilla.org/kb/Could+not+initialize+the+browser+security+component Check the permissions of the cert8.db and secmode.db files in the Firefox profile folder. You can also try to move the two files to another location (folder) to see if that helps. You can use this button to go to the Firefox profile folder: *Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder) If this didn't help then try to create a new profile. 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 careful not to copy corrupted files. *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox