IChat not letting me join multi-person video chats?

my ichat only lets me join single person video chats. whenever i open my network status on the connection doctor it always says the port is restricted and that the computer's network setup includes one or more devices that are not fully compatible with audio and video chatting. It says its because of slow connection, but my internet has always been very high speed and everything else on my computer that uses internet works at just the same speed. the server is slogin.oscar.aol.com, the port is 5190 and require SSL is checked. i have restarted my modem (linksys), restarted my computer (macbook pro, ichat version 5.0.3), and switched the port to 430, but nothing works. what should i do?