I thank you! The original problem turned out to be a loose PCI-E power connection on the GTX480! So the 680i was looking at the 8800GT in a secondary slot as the primary VGA adapter. Which since a later BIOS revision from EVGA deemed not to be an acceptable practise and this is the reason I was getting a code 5d. As far as GPU temperatures go, both the GTX 480 and 8800GT are around the 40 degree mark when playing Mafia 2 at the moment. Quite eager to try the two Batman games to see how this system fares now!