Recently I was having problems connecting to iChat, was getting random disconnections from AIM, and I couldn’t video chat. I did some research on various message boards, where I discovered a consensus that port 443 is the most stable for video chat. My iChat preferences were set to port 1053. To view your iChat port settings, simply launch iChat, then browse to Preferences > Accounts > Server Settings. There you will see assigned ports.
Everything is working now! I was pretty excited to have worked it out.