Does your manual indicate you need to hook up an audio cable from the capture card to the sound card? One of the PCTV cards I saw requires this.
Pretty hard to get a manual from web. Here is example that requires cable. Probably not the same as yours.
ftp://ftp.pinnaclesys.de/Manual/Medi...TVCenter%20V.4
and then look at PCTV100i_EN.pdf, as an example.
If you don't need to do this or if you needed to and already did hook it up then did you try to see if any of the selection in alsamixer needed to be unmuted? I'm not sure if one of the mics or lines might work.
If you are running kde, run kmix and choose the input tab. Does playing with any of those settings help?