I received an email from EP, who had problems running the new Expendable demo (story) on his Voodoo card, and the reply he received from Rage to his inquiry about this indicates that the demo will only work on a 2D/3D combo card, not systems with a 2D card and a 3D card (this will not be a limitation of the full game). Here's the skinny:

The Expendable Demo will not work on machines which have a proper 2D only card in conjunction with a 3D card. This is a known bug and has been fixed for the full version of the game. Sorry, but you will not be able to play this demo.