Are the power connectors firmly connected to the graphics card? Is there any popup from nVidia stating a power inefficiency? And how bad are the stutters? What's your FPS in the games you're encountering trouble with?
The stuttering is pretty bad. Messing with the graphics quality doesn't seem to affect it at all. The framerates bounce from 60 to like 15 and back. I am playing with vertical sync on. I'll try looking at the power connectors and reinstalling the drivers.