In the absence of anything else working - I have a different SB card and had a similar problem, only with WINTV i.e. the sound card worked to give normal Windows noises (dings, tadas, etc) but nothing came through on TV. After much hair tearing, I discovered that there was a Sound Control Centre task bar which lived out-of-sight at the top of the screen which incorporated a MUTE function!!! This it would do, on its own, with no indication on the visible screen. Probably nothing to do with your problem but it might be worth checking.