Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of your add-ons is causing your problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).

• Don't make any changes on the Safe mode start window.

See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

If you have Adblock Plus installed, open its Preferences window, and uncheck this line: "|http://s.ytimg.com/*"

Go here first: http://www.youtube.com/swf_test.html Then: "Right click on the player > click Settings > Disable Hardware Acceleration > Refresh your Internet Browser"

I do have Adblock, but disabling doesn't solve the issue. Youtube pages stay completely blanc (white). There is no "|http://s.ytimg.com/*" filter entry either to remove.

@chgojdc: Going to the link you provided still gives me a completely white screen. No player to rightclick. Rightclicking gives a menu without anything related to setting, just like rightclicking normally on a website.

Do you have the Flash player installed (Tools > Add-ons > Plugins)?

• http://www.adobe.com/software/flash/about/