Go LW>Tools>Options>Advanced>Firewall and see whether there is a port number in the filed of the listening port.
In any case, deleting the LW preference folder to prevent any corruption and/or misconfiguration of the client as possible cause might be another step you could take. How to do so, you can read here in Point #2 & 3 in Fixes for Limewire:
http://www.gnutellaforums.com/showth...threadid=36420 