Do you know if it was the actual GPU or something in the card?
It could be anything, from all I know.
Here's what happend:
I was playing a heavy game (Crysis first time / BF3 now) when suddenly the game froze and alternating grey and black lines appeared on the screen. Upon restart, the computer boots, but no image is transfered to the screen. The fans go (including the one on the graphics card), and I hear the post beep. But the VGA LED lamp on the mobo is on, indicating an error on the graphics unit. I tried switching the card to a different PSI-slot, but same result. When I take out the card and run with onboard CPU graphics, everything works well.
I've got some theories:
1) Defect graphics card(s). Possible, but unlikely, since it has happened twice now.
2) Defect PSU. Could possible fry the card with over-voltage or something. But shouldn't that affect other components too?
3) Defect mobo. I don't know about this one. Wouldn't this affect some other stuff as well? Like not being able to run anything at all.
4) Defect RAM. I have no idea how this would affect the graphics card, but who knows.
The other components shouldn't really matter.
5) Overheating due to bad airflow. But wouldn't the computer crash before this happens?