I looked at the post on 275.50 drivers and found this:
Hi, Nvidia has released the Beta 275.50 driver for Windows XP, Vista and 7. This driver is for GeForce 6 and higher desktop cards. It is identical to the 275.33 WHQL driver, except for enabling SLI on 990FX, 990X and 970 AMD chipset motherboards, and providing 3D Vision performance improvements in Duke Nukem 3D with 3 or 4-way SLI. The driver package also contains the 9.10.0514 PhysX drivers.
A lot of people in the 275.33 thread saying it is bad. So I think I'll go with the 270.61 drivers first and see if things clear up.