Its the NVIDIA driver in all probability. The latest NVIDIA drivers for Windows Vista are
all beta. They release one every month. They do tend to do that so I suggest you fill up the form you get on their site where you downloaded the Vista Driver.
New drivers come out every month so keep updating regularly
This happened to me too for 2 games and I wanted to play them badly so I moved to XP just for that reason for some time
/ 
