Try this, open your Tv program.
Open your audio mixer i.e kmix, aumix or other, and check the line In level. If the line In is muted, unmute it and move the slider up until you
hear sound from the tv card. Most tv cards will use the line In channels
when playing audio.
I don't have the tv card you have, mine is is a winTV from hauppauge and it uses the bttv driver. The above instruction has worked for me when I didn't get audio from the tv card. Hope it works for you.