i've been doing stuff with school networks (being a student at one) for the last 7 years! I can only now get on msn messenger because i have the teacher-level internet ip address... there's a slower connection for students with everything blocked, and a faster one for teachers unblocked!!
The answer is - if ur admin's disabled the port, there ain't no way ur gettin in through!
(Incase you don't know, firewalls prevent access through certain ports. MSN messenger is probably disabled through that!)
Hope that's a decent explaination even though it's no help!!
Hob