YES - I am also having this sound issue, running Snow Leopard on a 2010 i5 macbook pro, maxed out with 8gb RAM and 1tb HD, everything on my mac runs fine (apart from an over sensitive touch pad which seems to push all apps off screen randomly), but I use this mac professionally everyday. The sound problem is SOOOO FRUSTRATING as I use both Facetime and Skype to communicate with family and friends across Europe.
As discussed throughout numerous community forums, the usual problems arise, conversation starts fine, then the recipient cannot hear my sound, usually after 10 minutes or so, then more frequently after that, until it does not work at all (during the same session). I have run disc utililty and repared permissions (whatever that is) and also experimented with the volume. No luck.
Any suggestions most welcome.
This sounds like something similar to https://discussions.apple.com/thread/3388112?start=105&tstart=0.
Try turning down the speak volume (System Preferences->Sound->Output->Output Volume) or the microphone gain (System Preferences->Sound->Input->Input Volume). Do this on both sides of the call.