nVidia 6800GT...Blank screen after changing resolution

I'm having a problem on Vista 32 with an nVidia 6800GT connected to my
Pioneer Plasma. When I change the resolution to match the native 1280X768 32
bit color of the plasma I get a black screen and my plasma says it cannot
display the current resolution. I keep expecting Windows to confirm the
resolution for 15 seconds and then revert to the original setting, but I can
never get the display back after that. I've booted into Safe Mode
successfully and removed the driver and forced the resolution down to
800X600, but as soon as I boot into normal mode the same thing happens again.
I've been forced to wipe and reinstall just to get Vista usable again. I
get the same problem using the Vista built in driver and the Vista beta
drivers from nVidia.

The same hardware has worked perfectly in XP Pro...in fact, XP detected and
applied the native 1280X768 automatically.