You can check for problems caused by a recent Flash 11.3 update and possibly downgrade to Flash 11.2 or 10.3. *https://support.mozilla.org/kb/flash-113-doesnt-load-video-firefox *https://support.mozilla.org/kb/flash-113-crashes Start Firefox in <u>[[Safe Mode|Safe Mode]]</u> to check if one of the extensions or if hardware acceleration 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.org/kb/Safe+Mode *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes