Just a recommendation for people out there, I know you don\'t have the choice of what brand your school uses for their routers, and it might be an intentional blocking issue compared to tweaking needed to be done, but I just wanted to state that Linksys routers really pwn when it comes to NAT. No forwarded is needed for any application that is client only based. So for that reason and many others, I just want to recommend Linksys routers to anyone out there that has a choice.
I hope you are able to fix your problem. Some people end up having to make a tunnel because their school only allows certain ports used, and I\'m not even sure if tunneling would work in this case.