Well, I've just about run out of ideas. I did a bit of googling, and found a couple of other people having problems with this board & sound (sorry, second one's in German)...
http://www.linuxquestions.org/questions ... did=325515
http://www.overclockers.at/showthread.p ... id=1825307
Is this a machine you've built yourself ? There were some threads on a couple of sites that claimed sound wouldn't work at all on this board unless you have a power supply that puts -5v on pin 20 of the connector, but then some other people disputed that - might be worth checking the specs of your PSU connector and the mobo.
Is there anything in the BIOS setup that allows you to set the mode that the sound is operating in ? If so, check out all the options - you never know !
Failing that, my advice is go get yourself a real Soundblaster and disable the onboard one. I know it's admitting defeat, but at least it moves you forward... and if a fix for the onboard one does eventually appear, you can move the real card to your next project machine