There has been a lot of people posting problems running Battlefield 3 with an Nvidia card, specficially the GTX 560Ti.
Something doesn't sound right - if it really was a driver problem, then I would expect a great variety of issues with a broader range of cards.
So I ran SpeedFan just to see what was going on:

I jumped in and out of the game a few times and you can clear see when - as soon as I quit the game the heat drops off very quickly.
So my question is:
- What / where is Temp1, Temp2 and Temp3 on the card?
- And what range should I be aiming for?
- How hot must the card get before Nvidia will crash to desktop?
- Does Nvidia write to a log file (or similar) to tell you why it has crashed to desktop?
+70 degrees sounds awfully high. Speedfan suggests that anything over 50 degrees is too hot.
Update
Sorry, just to clarify, if I run Battlefield 3 at full screen, high settings I get about 4 - 5 minutes of play and then the game crashes. I get maybe 12 - 15 minutes if I run the game at 640 x 420 windowed. Graphics card is GTX 560Ti, OS: Win 7 64bit. Same problem running Nvidia drivers version 285.38 & 285.62