I found this at the ATi site, thought it might help some folks:
DirectX/Direct3D Applications - problems when monitor type is "default" or "unknown"
You may experience problems attempting to run DirectX/Direct3D based applications if the monitor type is set to "default" or "unknown". Symptoms may include, but are not limited to:
the application exiting to the Windows desktop when run
poor performance when running the application
hangs or error messages when running the application
A variety of DirectX/Direct3D based programs (ATI's RAGE Dawning Demos, numerous games, etc.) may experience these symptoms.
To resolve this issue select a Windows provided monitor type which matches the monitor in use or check with the monitor manufacturer for an appropriate monitor INF file.
If you still continue to experience difficulties please provide the following information:
the make/model of monitor in use
the monitor type selected in Windows itself
the name of the application in use
a description of the exact issue being experienced
a completed ATI Problem Report
INFO-BASE file # 3579
