The airport base station settings would probably have something to open and block ports, but I've never configured one. Port 6346 should be "forwarded" i.e., to allow messages from outside to pass through the station to your computer. They are probably being blocked. You could scroll through the LimeWire Preferences->Bug Reports->View Example to find the line that says "Received incoming this session: true" (yours will show "false" if incoming connections are blocked).

Well late here too. Cheers