Screen out of Range (below 60 Hz) when starting Media Center in Vi

When I try to start the Media Center in Vista Beta 2 (5384.4 German) then my
Screen tells me, that it is out of Range (49.8 Hz) which is odd, because in
the Displaysettings if setted it to 60 Hz.
It only happens when I start the Media Center, and switches back to 60 Hz
when I exit the Media Center (by pressing Alt-F4)
The most oddest thing is that when I press the Windows Key on my Keyboard,
the Screen switches back to 60 Hz, and in the Background I can see the Media
Center Setup running, I also can select things on it, and klick the Buttons,
but as soon as I've klicked the Media Center ore one of its Options or
Buttons, the Creen goes out of range again. I've not found any place or hint
what to change, to keep Media Center to switch below 60 Hz.

I have a Geforce 6800 GTX with the latest NVidia Forceware drivers for Vista
Beta 2
The Screen is a Acer AL718 LCD (installed as Super-VGA 1280x1024)

Please help, and ask, if I've forgotten to mention something.

I eager to try the new Media Center...

 

I had a similar problem. For me it was because the monitor driver was for a
non generic pnp monitor. Once I changed it for the correct flat panel
driver, it worked OK.

Stuart