Richard...too bad you couldn't save it.
Curious...were you rendering something when you problem started? Mine started right after finishing a 30 minute render.
I noticed the system was sluggish so I rebooted and after that I started getting the dreaded blue screen of death. Every BSOD was a different error code. Once I was able to uninstall the 190 drivers and switch back to 186.18, the problem was gone.
I knew something was buggy with the 190 drivers when Photoshop reported that my video card would not support Open GL.
For now I suggest while running 64 bit Vista with a Nvidia card, use the 186 drivers until they work out the bugs.