Hmm, to be honest, I have no idea what kind of problem that would be.
This is the first time I've heard of that issue, and I don't know what would cause it. But since the demo and final version use almost identical code, I would expect an issue with the demo to reproduce in the full version.
If you'd like, you can send a dxdiag.txt to
[email protected] and we'll look at it. (To make a dxdiag.txt, click Start->Run, type in 'dxdiag', and then click 'Save All Information' in the DirectX diagnostic tool that comes up.)
Thanks!
-Hiro_Antagonist