Trying to connect at schools is an issue for many people b/c schools often block p2p use, else they'll at least have a firewall. When LW is open, click Tools-Options & go to Bug report & click for an example. In the window that appears scroll down to the part that says: "Received incoming this session". If it says 'true' then LW has no problem with firewalls. If 'False' then you have a firewall issue.
Do you have XP's firewall on/off. There's instructions on LW's website about how to allow LW to get thru. Have you updated to XP SP2?
http://www.limewire.com/english/content/firewalls.shtml
Which port is Kazaa running thru? You could even try the same port.