Downloaded the Forceware 91.47 drivers on Friday night for my 6600GT. Not good. Most annoying was that Windows wouldn't remember my display resolution settings, so every time I restarted, the resolution would return to default 800x600 with a 60 Hz refresh. Didn't make a difference if I used the new Nvidia control panel or used the older style control panel. Also there were some weird things with my sound (original Audigy), like not playing things out of my rear speakers. The new control panel interface doesn't work right either -- despite having checked the box to prevent displaying refresh rates my monitor does not support, it listed refresh rates going up to something like 200 Hz.
I uninstalled, went back to the prior Forceware version 84.21, and all the problems went away.
Anyone else having problems with Forceware 91.47, especially with a 6600GT?