Cheese Panzer

OK, I downloaded the demo. It ran once, but very slowly. After the first time it refused to run, always giving me a: DirectX "dderr_unsuported" error during the "calculating supply" phase of loading the first turn. I've updated my drivers, installed DirectX 9, and reloaded the demo several times. Nothing works. I've already pre-ordered the game and I'd hate to have it not run on my machine. HELP!!!