The title explains it, really. I can run the demo and the tutorial with no problems, on any graphical settings I choose, but neither the main game nor the preview will load.
I click on New Game->Start Game or Preview, and the screen turns black and stops responding.
I'm running Vista Home Premium 32-bit, and I can never remember my hardware configuration, but I can run the demo and tutorial at 1680x1050 on the highest setting. Sam & Max and SBCG4AP run with full settings, too.
EDIT: I have tried reinstalling, restarting, the usual. I have not tried re-downloading the installer yet, as I am on a restrictive internet plan, and I need to wait for off-peak time.
EDIT 2: I downloaded the installer again, and reinstalled, and it works fine now. Thanks for all your help, everyone. :P