IChat Communication Error : No response from invitee

Hello,

Could really do with some help here. We bought my mum an IMac on the basis that video conferencing is really easy and that it would be no trouble to video chat with her grandson (apart of course the difficulty in understanding the babbling of an 8 month old!).

We bought a MacPro for our end, and it worked perfectly well when both computers were running in the same room as a test. Now that we're home again we keep receiving a communication error whenever we start up a video chat. The text chat works fine and we are able to see that she is online and available

Both accounts are on AIM, and are running Leopard on either an IMac or MacPro.

When I start a video conference the request pops up on her computer, and she accepts the call. At this stage I can still only see myself on the screen and a note saying that she accepted the call. After maybe 20secs another screen pops up returning a communication error saying that I did not receive a response from her even though she's accepted it!

This is truly maddening

My mums IMac is connected to the internet via BTBroadband home hub wireless modem, and I'm running the MacPro on an NTL Broadband Internet modem connected through a Linksys WRT54G v7 router and ethernet cable.

Any help would be really appreciated as the main reason for going with Apple was the video conferencing!

Thanks

Ian