windows live messenger/firewall problem

hi, I’m having a problem with windows live messenger on my laptop. You see I’m trying to access the windows live messenger using a wireless internet connection but I can’t connect to it because of a firewall problem I believe. I’m using windows xp sp2 with windows firewall, I can’t connect to it when I’m at school and I’m not sure what to do, because other people with laptops can connect to it. I know it’s some kind of an internal firewall problem or something but not sure how to fix it. I did open windows firewall and changed the exceptions for windows live messenger to accept port 1863 but that did not resolve the issue.

If anyone can help with this strange problem that would be awesome.

Thanks for your time.