Start Firefox in <u>[[Safe Mode]]</u> to check if one of the extensions is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes). * Don't make any changes on the Safe mode start window. * https://support.mozilla.com/kb/Safe+Mode If it does work in Safe-mode then disable all extensions and then try to find which is causing it by enabling one at a time until the problem reappears. * Use "Disable all add-ons" on the [[Safe mode]] start window to disable all extensions. * Close and restart Firefox after each change via "File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit") * https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes ---- Create a new profile as a test to check if your current profile is causing the problems. See: * [https://support.mozilla.com/kb/Basic+Troubleshooting#w_8-make-a-new-profile Basic Troubleshooting: Make a new profile] If that new profile works then you can transfer some files from the old profile to that new profile (be careful not to copy corrupted files) See: * http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox