Vista - Windows Media Center - No Sound on playback or live TV

I have Vista Home Premium installed and everything used to be working
well. My video card died and it has been RMA'ed and in the meantime I
instaled my old video card. Everything works as it should except in
the Windows Media Center. It starts up properly with all the right
sounds and I can hear when I move to the different menus. However
when I go to live TV or try to play a recorded show, I hear 2 seconds
of sound and then silence. I can't get back any sound until I exit
the Windows Media Center.

I have checked everything, drivers, connections, sound setup and
evething works fine except the Windows Media Center. Anyone have any
suggestions? If I have no fixed this by the time my video card comes
back it will be another format drive c: :-(

Al