why won't LimeWire allow connections to lower ports?

I am currently running mac os 10.2.8, using the standard Limewire download (Vers 4.0.6) inside of a university network. Because of this, the upper ports, like the one used by limewire, are blocked. To circumvent this, I ran a port scanner (in network utility) and found that ports 21 (FTP) and 80 (standard web pages) are both open. I have closed all other applications that may be using those ports, and my firewall is currently turned OFF. However, even though my port scanner still reads these ports as open, LimeWire gives me a message saying that they are not available. WTF!! all my friends use programs like bittorrent, emule, etc. and they have changed their ports to get around the security, and LimeWire just has to go and be a B***H! Can anyone help me?
Frank