Start Firefox in <u>[[Safe Mode|Safe Mode]]</u> to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance). *Do not click the Reset button on the Safe mode start window or otherwise make changes. *https://support.mozilla.org/kb/Safe+Mode If it does work in Firefox Safe-mode then disable all extensions (Tools > Add-ons > Extensions) and then try to find which is causing it by enabling one extension at a time until the problem reappears. Close and restart Firefox after each change via "File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit") *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes ---- 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 There may be extensions and plugins installed by default in a new profile, so check that in "Tools > Add-ons > Extensions & Plugins" in case there are still problems. If the new profile works then you can transfer some files from the old profile to that new profile, but be careful not to copy corrupted files. See: *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox You can also try to reset Firefox: *https://support.mozilla.org/kb/Basic+Troubleshooting