Tonight something worked that hasn't worked in a while. While my wife was using iChat she got a invitation for a Audio chat, and it worked.
This is the first time that this has worked since we got Vonage. When the Vonage ATA was connected in between our broadband connection and the Netgear firewall, none of the Audio chats worked. I think that it was because the Motorola VT1000v was blocking all connections to port 5160 (SIP), but not rejecting them. Then iChat was timing out trying to start the connection.
Now with the new Linksys WRT54GS, these connections are being rejected. Then iChat uses the AIM connection to do the audio streaming.