Hi,
I have seen one other Thread in which when adding in or starting a VPN causes iChat in Lion to Fail.
I have known for a long time that iChat needs to have one IP only.
Connecting Wifi and Ethernet will cause issues when it comes to Audio Only or Video Chatting.
(iChat 1 through 5 seems to cope with a double Internet Connection during the Login and Text chatting parts).
There was an issue in Leopard (OS X 10.5.x/iChat 4.x) where, if you turned On System Preferences > Sharing > Internet Sharing then that computer's iChat could also "See" the Internet Connection of the Shared Device.
I have never created a VPN for myself and would be lost in suggesting any steps to take.
9:06 PM Tuesday; August 23, 2011
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb( 10.6.8)
Mac OS X (10.6.8),
"Limit the Logs to the Bits above Binary Images." No, Seriously