Sound problems

Iv'e connected my comp to the tv..great..lovely pic and graphics..set the sound on the tv and alls well on windows media player lime wire and other sites.....When i log in to SL there is a clicking coming from the tv speakers at odd intervals and no sound....I can get the sound momentarily by switching the tv from analogue sound to digital and back again,then it clicks and the sound goes......grrrrrrrrrrrrrrr. My system is running an intel dual processor, geoforce 8800gt graphics card and sound blaster x-fi extreme music sound card.
As i say on all other sites and applications the sound works well.
If i revert to just using my comp as usual ( i.e. not connected to the tv ) everything is fine Can anyone help PLEASE !

How are you connecting the pc to the TV (what connections).