You can also turn off the OSX firewall, or at least set it to allow Gnutella/LimeWire

System Preferences->Sharing->Firewall->New->Port Name->Gnutella/LimeWire (6346)

You can also add other ports here, like 6348.

When checking my ISP, I also try port 20300, in case they just block the usual gnutella ports.

Whichever port you use, set the same one in LW Preferences->Advanced->Port and Firewall

(If you use a router, you'll also have to map those ports in the Advanced->Port Mapping or Port Forwarding sections --the details depend on the router but should be covered in a manual or on-line docs)

Cheers

if you need to try the latest LW version, look at http://baghira.han.de/~jum/LimeWire.html for the jum builds that Jens-Uwe Mager has generously made available for OSX users.