It means that LW's default port is being blocked. Possibly by your school. Have you made sure your firewall's configured properly?
http://www.limewire.com/english/content/firewalls.shtml
(only run 1 firewall at a time or you'll have problems)

You could try changing ports. There's a bit of a guide to alternative ports here, check out LOTR's post #6.
http://www.gnutellaforums.com/showth...274#post189274

You should probably go & see your school's computer admin. Find out if they're blocking or filtering p2p.

Good luck