[Ti] iChat v Yahoo! Messenger

[Dr. Trevor J. Hutley]

I have never been able to get iChat to work from here in Saudi 
Arabia.  The moment I return to Switzerland and connect via ADSL, it 
works perfectly.  I had assumed that it was some nation-wide 
configuration restriction here to prevent chatting.

My PC-user-friend stopped by this afternoon, and asked if I had 
Yahoo! Messenger, as he wanted to use my dialup to exchange some 
messages.  So I quickly downloaded Yahoo! Messnger for OS X, launched 
it, and it worked straight away..........

So what could be the explanation for this?
What is it that iChat does so differently to Yahoo! that it does not work?

Does anyone have any idea about the workings of iChat and Yahoo! 
Messenger, that could explain this unexpected result?

regards,  Trevor