Have you tried the rear card connections? It has coaxial S/PDIF connectors which may work better. According to the link you provided, the front panel (
http://www.soundblaster.com/products/enlarge.asp?product=16559&img=Platinum_fatal1ty_champion_series/pop_IODrive.jpg&alt=) says "Stereo Digital/Analog", which may mean it is limited to stereo - check the manual to be sure.