erm. the main point of my post is not Nividia vs ATI.

it's the very real possibility that the entire G8* series of GPU's are faulty. Right now Apple and HP are reporting large numbers of faults and are offering repairs on affected units. Right now, it's mainly Laptop based chips, but there are predictions that we've just not reached the failure curve for the desktop units as yet... (Laptops under go more heat / cooling / heat / cooling cycles than desktops...)