Makes and models of routers and modems.
I had worked out the Macs were fast enough for Audio chats.
http://docs.info.apple.com/article.html?artnum=301050
What is important now is Internet Speed and some settings.
In System Preferences > Quicktime > Streaming what have you got the speeds set at ?
The Automatic Setting (In Tiger) is read as a 0 (Zero) by iChat and will effectively stoop it working.
The Intranet/LAN speeds is also misread by iChat.
For Video chats we suggest setting it to 1.5Mbps almost no matter what your Internet connection speed is.
It needs to be set at least as fast as your download speed so that it does not cap other Video streaming.
You seem to be up on ports and stuff in the Routers/modems.
That leaves the Mac Firewall if ON
This will need you to set the A/V ports for iChat. Audio and Video use the same ports and there is no Preset in Tiger for this.
7:52 PM Sunday; January 27, 2008