iChat promised a lot but so far, it has not delivered as good as it should. I donʼt know if it is because I am in Europe or what, but it seems like iChat works in some cases and in others not. Sometimes one gets sound to work, sometimes video and sometimes not. Text works all the time, at least! But aside from that, it seems like it depends on the internet service provider or the router and/or the firewall and what not, but it is too much of a hazard to rely on, alas.
It has been like that since I first used iChat - was that on Panther? It has been like that on Tiger and it is still like that in Leopard and it has been like that when I lived in Portugal and it is like this when I live in Norway. It was like this on my old G4 and the same on my iMac G5 and my iBook and now on my Intel iMac. Now it works for me, but then my sister in Sydney has problems. Some of them I have managed to solve, but other persist.
When it works, it is the best out there, but unlike Skype and unlike Yahoo Messenger and aMSN and whatever instant messenger supporting video and/or audio, iChat doesnʼt work all the time.
Why it is like this, is beyond me and I have tried every trick in the book and taught some of them to others.
People at Apple, do you read this? Hope you can do something about it. It should be plugʼnʼplay but too often it is not - and I am not the only one having problems. Go to Apple Discussions to see...

Sorry to hear about your problems, wilf. It has always worked for me. I never fiddle with firewall or router settings either. Perhaps that's the key...