HI,
As this is Snow Leopard it could be FaceTime or iChat that you are using.
I am presuming iChat.
I take it that the Video feed for your end (the Pic-in-Pic bit) appears to become frozen and you and your Buddy can seemingly Audio Only chat over a still pic ?
I would try a PRAM reset.
Shut down the computer.
Restart it holding down Apple/CMD ( or ⌘)+ALT( ⌥)+P+R Keys until you have heard three Start Up Bongs.
Are any other Video able app having issues ?
Photo Booth ?
iMovie ?
9:51 PM Wednesday; July 18, 2012
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Lion 10.7.2)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
"Limit the Logs to the Bits above Binary Images." No, Seriously