What kind of videos are you referring to? Is a Flash player used to play the videos? ---- 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 *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes You can check for problems caused by recent Flash updates and try these: *disable a possible RealPlayer Browser Record Plugin extension for Firefox and update the RealPlayer if installed *disable protected mode in Flash 11.3 and later *disable hardware acceleration in the Flash plugin *http://kb.mozillazine.org/Flash#Troubleshooting