I recently started having a problem using firefox with youtube. I installed the Tamper Data add-on and restarted. After I restarted no youtube videos would load. They just sit with a black screen. I've tried clearing all cookies and restarting firefox. I've also tried disabling the Tamper Data extension but it does nothing. I updated adobe flash player as well. This does not happen on any other flash-based websites. All youtube videos work perfectly in IE and chrome. Thanks.