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
![:)](images/smilies/msn_happy.gif)
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
![;)](images/smilies/msn_wink.gif)