Found this thread amongst others whilst searching for problems regarding the 8800, seems like I'm now a victim to the dreaded timebomb with this graphics card
The same drill here, my early 2008 24" 3.06Ghz with 4GB ram installed has worked flawlessly for just over 3 years then two months after applecare runs out, boom!
Only had the machine turned on for a few minutes, opened iTunes then Safari and the screen froze and the track playing went nuts and soon stopped altogether. With no keyboard or mouse response I shut down, waited a few minutes then restarted only to be greeted by the green and purple artifacts/split screen. After a number of attempts to restart, unplugging etc, and getting nowhere I did some quick searching (phone at hand!) and soon discovered this to be quite a regular occurrance with this spec of imac.
I went through some software tests with apple support over the phone, (they kindly agreed to try to help even though the applcare had expired) it was agreed that the card was likely to blame so I booked it in for a genius bar appointment.
A few tests later I was then quoted just under £260 to repace the card, I declined, walked out and decided to think about it.
Now after hearing of replacements failing and even second replacements, I'm at a loss what to do, I don't want to pay money for another card with just a 3 month guarantee only for that to potentially (and now by the sounds of it likely) die too. Nor do I wish to keep sending it to Apple for replacement of other parts which again seems likely and has happened in a number of cases.
I will speak to Apple customer services and hopefully know more about what to do next but man, finding this out has really ticked me off and left me computerless.
