computer problem casued by playback attempt

I clicked on one of the Google videos to play back, and it played ok.
But now my computer (MAC g5) has been affected. Even after quiting my
browser, things have gotten jerky on my system -- for example I edit
videos with Final Cut, and all of a sudden my video play is jerky.
This never happened before but started happening right after the Google
video playback, so it must be connected. I've tried repairing
permissions and trashing preferrences but it is still jerky.

What is going on?