Most high speed connection devices have internal NAT firewalls. So this may be where your problem is.

Can you give us a total description of your set up:
1. Connection type? (eg: dialup, broadband, cable, etc.)
2. Modem & router brand name & model numbers?
3. Where are you trying to connect from (home, school, work, etc.)?
4. What version of Limewire (LW) & Java do you have? (Go to LW's menu Help>About LW...) Will show both LW & Java version.
5. Who is your isp provider (Internet Service Provider)?
6. Are you sharing the connection with other computers or p2p sharing programs? If yes, please give details of set up.
7. Do this simple test for us. Using your browser go here: http://www3.limewire.com:6346/ The page should say 'Your test worked!'. What happens when you go there?