Howdy,

in System Preferences/Sharing You can select the Firewall button and then create a new port setting using "other". Use these spaces to set TCP and UDP ports to 6346 and then enter the discription box as LimeWire. That should do it for the Mac. If you still have trouble, try turning off the Mac firewall. If you are using a router, check the router utilities for firewall settings. the port forward website was helpful for me. it has Limewire settings and router information.

Hope this helps