Error trying to load Demo

[AnubisArc999]

I have tried 3 times on Steam forum to get help, but no one offers anything useful.

C:\work\skyfallen\tbm\BMRender\rmode.cpp(1633): DirectX call failed -1, -1, E_FAIL (An undertermined error occurred inside the Direct3D subsystem.

Obviously, if I can't get the demo working, I wouldn't buy the full game game.

I have running Win Vista 32bit with an ATI Radeon HD 4850.

On Steam forums, most of the responses/solution to others with this same problem are related to nvidia cards drivers, but obviously I don't have an nvidia card and thus those don't help me.

I am pretty sure I want this game, but if I can't even get the demo working, then no point getting the full game.