I take it you've fiddled with the line input configuration and then all the volume controls?
(in other words, you're sound card is configured in SD?)
I have absolutely no sound using the SD demo. Wondering if this was normal or is something horribly boned? I'd hate to fork over the cash and have it not work at all. Ideas, thoughts, I'd take a poem at this point if it fixed the issue!
get back with us so we can help ya out here!