I'm having this issue with my 24" iMac, with an 8800GS, and a s.8 ghz Intel Core2Duo. The first time the graphics card went out was late April. Bought a replacement part out of warranty. The card died again, accompanied by artifacts, failures to boot into the OS, etc about 2 weeks ago. Again it was replaced, this time by the part warranty. Last night the card died yet again! 3rd times the charm? Hopefully, even though I am out of my initial one year warranty, Apple will replace my computer. It's quite frustrating. Any advice or info?