Well if itunes visualizer causes the same thing to happen it's quite obviously not a SINS-problem...
having said that.....what exactly are your computer system specs? Hard to point the finger when I don't know what I'm pointing at....eh? hehe
Without anything else to go on (at the moment) I'd say that it sounds like a power supply issue (power supply going bad, or not supplying enough power when video is intensively used).
Give me more info, and I'll be able to help you better...
thanks,
the Monk