Since you mentioned you tried the video card in another rig and it crashed again due to the drivers i would suggest you read upon TDRs.
For troubleshooting try rolling back to an older driver version. If you don't remember which one was stable then try 295.73 and test using the GTX 570.
Note that you are not alone, there are a lot of people that are experiencing this problem it's just that the reasons why the TDRs happen vary a lot.
nvidia did not recognize it as being their issue, maybe the reference design works fine and it could be a problem caused by their partners. Personally i'd advise anyone to steer away from nvidia products for a generation or two until they fix their problems but it could also be a bias on my part, maybe the percentage of cards that are defective is not that big, it just seems big because nvidia sold more of them than AMD.
I think that did it... Increased the TDR timeout value and played for 2 hours non stop, let it idle ingame for 1 hour and then played another two hours and it never crashed. It was with the lid off so tomorrow I'll test again with the lid on, temps didn't seem any different but I think I might have a heat buildup issue too.
The 570 is toast though... it crashes within SECONDS even with the older drivers and it doesn't recover... actually I might have been misleading, it never recovered, I had these kind of crashes back then when one of my 8800GTXs was dying and you could "save it" by alt tabbing real quick when it seemed a crash was imminent... with the 570 it just black screens and locks up.