Check the BIOS. I don't know about the Deluxe board, but the vanilla board has a BIOS setting for Auto, Normal, and SLI. If the guy before you set it to SLI, that may be your problem. Also check the EZ Selector card and make sure it's set to single card.
*edit* D'oh. Guess you can't check the BIOS without a screen... Move along folks, nothing to see here.