you might also want to check out other ways of connecting to irc servers (like, if you can ssh into a machine at home that's connected, that could work...)
my guess is that they blocked the standard ports for irc (6000 - 7000 or so...). You may want to look into irc servers that use non-standard ports. I know on undernet there are a few servers that have some ports in the 4000 range... this may get you around the firewall.
something some people at my school have done to get around the irc port blocking is they go to a public proxy server. Only problem is a lot places that host IRC block those servers so it hard to find one that will work since most of them have gotten black listed