I have the same issue with GTX 660, but didn't have it back when I was using GTX 460.
When in full screen mode, the window usually goes black the FPS drops immensely, then it goes back up after a few seconds.
The error that occurs is a pop up bubble on the lower right of your desktop with the description: "Nvidia display driver has stopped working and has successfully recovered."
However, if you play in full screen mode, you won't see that error since the pop up bubble disappears when you alt tab out. If you're running in windowed mode, however, once that issue pops up, you will see the notice bubble appear in the lower right of your desktop.
I've tried googling the problem before. A lot of people have the same problem with various games. There are a bunch of different "solutions" that different people have tried, some are successful, some aren't. It seems that no one has a real universal solution to it yet. I've tried a few different things, but the problem is still here.