I have had an ATI 9800 overheat and lock up a machine. I had to remove the card directly above it and leave the slot cover off to keep it cool enough. This started happening after it was 2 years old.

When I tried to replace it with a new 9800 or x800 it was almost impossible to track one down.

Are you using the older G5s or newer with PCIe slots? What model of card has died?

Cheers

Toby