Please help with 4870!!

I just built a new computer and from day one games where just going to a black screen or the screen would corrupt out after a short time, in crysis it would do it while loading the game or in the game itself, in half-life2 it would do it in game, and with oblivion it also does it in game, only hitting the restart button fixes it. I thought it was the video card at first a sapphire 4870, so i RMA it. But when i put the new one in the same exact same thing is happening. The temps arnt to bad under 50c idle and and upto 85c in crysis but under 70c in all other games under load. They will play just fine for a while but then just quite and sometimes the sound will loop or stick, and other times the game music just plays on. Windows runs flawlessly. I have reinstalled vista and the 8.8 ccc drivers to no avail, i went back to 8.6 drivers, what the card came with but that didnt work either. Since the symptoms are the same with both cards i dont think thats the cause. My specs are

Asus P5Q-pro MB
HD4870 sapphire 512mb video card
antec tpq850 850W power supply
core duo e8500 3.16 processor
4gb gskill ddr2 1066 memory
WD 10k rpm hard drive
Windows Vista ultimate 64bit

If anyone has any idea that would be great cause i am at a total lose right now. And quite bummed.

tried driver update?

Anyone else know what that error might be trying to say?

I have absolutely no idea what that error message means.
Nevertheless I would do the usual drill:
1. run memtest86+ something like 8-10 hours to test the memory for errors. If errors occur, try increasing the voltage a notch and/or loosening the timings and repeat memtest. keep repeating until you'll get good or run out of comfortable voltage/timing options.
2. run prime95 to test the CPU for stability. remember to check the error notification option (or something). If errors occur, try increasing the voltage a notch and keep repeating until it gets stable or you run out of comfortable voltage range. mind the temps! use RealTemp for cpu temp monitoring.

Look into the overclocking section for more info about these programms and how to use them properly. There's a sticky 'core2 duo/quad overclocking guide' that will explain it in great detail and lenght.

If both come out just fine it could be mobo issue, not sure how to test for that other than changing the mobo.
It might be PSU issue as well, but I think that's unlikely. you have plenty of power and good reliable unit, but sometimes $#!+ just happens...

edit some typos, bet there are plenty still left though