Audio Problem

I'm a bit baffled with this one.............

This my current setup....

My shuttle reflexion has an optical cable going to my Audigy 2 NX that is plugged into my coolermaster PC. It allows me to use all my speakers on both pc's.

Heres what happens.......

I could be quite happily surfing the net on my Shuttle PC, listening to songs in Winamp..... and theres a click noise..... and winamp stops playing... its as if its been paused.... winamp is still functional but doesnt play any noise. So if you press ctrl, alt and del.... you can end the winamp.exe process.... theres another click noise..... if ya open winamp again... it play no problems.... then after about 60 seconds... sometimes even 10 minutes or so... its quite random... theres a click noise.. and the song stops playing.

I've tried reinstalling winamp... i've tried putting new audio drivers on..... i just dont get it.... i might try putting the Audigy2NX on the shuttle and run the optical cable from the coolermaster instead.