A False incoming response means something is blocking. If you're going to use your OSX firewall then make sure it's properly configured to allow LW full access: http://www.limewire.com/english/content/firewalls.shtml

By the way a Stealth port response means you can't do the port test properly due to a firewall. Better to use this one: http://www3.limewire.com:6346/ The page should say 'Your test worked!'. What happens when you go there?

What Modem & router brand name & model numbers do you use?