Screen never turns off
 

I have Vista pre-RC1 build 5536. This is the first build I've tried on this
computer. I dual-boot into XP, works fine. I have a problem with that the
screen never goes into energy-save mode. After the set time out (20 minutes)
the screen goes black, but the monitor is still on, I can see that the
backlight is on, and the LED shows that it's on.
I have an AGP ATI Radeon 9550 graphics card. I've tried both with Microsoft
graphics drivers, and ATI, some issue.

Thanks for any suggestions,
/Hakan