Unable to set graphics mode above 800x600 fs

I can't create a fullscreen graphics mode higher than 800x600 , I tested at 1280x1024, 1600x1200 and 3200x1200, all failed.

windowed works fine, tried variations of bitdepths.



Intel Core 2 Quad 2.4G Q6600
NVIDIA GeForce 8800GTS 320MB
ASUS p5K Deluxe MB
2G RAM
DIRECTX 9.0c August 5.3.2600.2180)
Windows XP sp2
GeForce Video 163.71 ( 6.14.11.6371)
Dual Screen
Blitz3d 1.99 (reports 1.98), previous version same fault.


test code
Graphics3D 800,600 ; works

Graphics3D 1280,1024 ; doesn't work or 1600,1200 3200,1200 etc.