Is my Graphics Card Dead?

[Slug For A Butt]

All cards have their own "little fan", doesn't mean it's not overheating. And just because you haven't OC'd it doesn't mean it's not OC'd as stock.
Without adequate ventilation and in the wrong environment, it's entirely possible that a standard card could be running too hot.
But as has said drivers may help too.
Just sounds to me like overheating, do you realise how fast a card or processor heats up? If your CPU isn't cooled right, it has a lifespan of about 10 milliseconds. Your GPU wont be too far behind.

[Gawain of Orkeny]

Sounds more like some kind of bug. Have you had your card checked. maybe its defective. What model 8800 do you have. I have one and it wont play VI for instance.

[Slug For A Butt]

Gawain makes a fair point. I don't know very much about anything specific (manufacturer/card specific). I wouldn't know the difference between a 7900 and an 8600 pertformance wise.
I only know a little about general issues that are relevant to any setup, and I would first update the drivers and then cool it as best you can. See if it helps.
Something else, has it been working fine for some time or is this something that has happened ever since you had this system.