when i try to play a youtube video it plays for only two seconds

when i try to play a youtube video it plays for only two seconds with sound but the screen stays black. it takes a little more time for the video to load also. then it crashes which ever internet program i am using. But whenever i turn off my plug-ins it works totally fine. how do i fix this? this has never happened to me before. i tried to uninstall flash player and reinstall but it fixes nothing, this has been going on for two days now.

i use safari and firefox and both dont work