I had a geforce 2 ddr overheating on me once during a brutal game session, it just shut of the signal output to the monitor wich went black of course, probably some safety function that turned of the power to the card when the gpu temp went to high, i just replaced the incredibly small fan with a better more powerful one and then the screen never went black again during gaming...

And that was a gf2, i reccon gf4 gpu's produce ALOT more heat.

:cheers: