Did you configure your firewall so it allows LW full access (advisable not to have 2 active firewalls b/c they can interfere with each other); Firewall configuration instructions (click on link)

Can you give us a total desciption of your set up:
1. 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?
2. What firewalls you have?
3. Connection type? (eg: dialup, broadband, cable, etc.)
4. Modem & router brand name & model numbers?
5. Where are you trying to connect from (home, school, work, etc.)?
6. What version of Limewire (LW) & Java do you have? (Go to LW's menu Help>About LW...) Will show both LW & Java version.
7. Who is your isp provider (Internet Service Provider)?
8. Are you sharing the connection with other computers or p2p sharing programs? If yes, please give details of set up.

I have a suspicion its related to using LW on 2 computers thru the same connection device. I'd tend to recommend using a different port. Is your modem/router set for UPnP? If not, then enable it or do a separate port forward for each computer using different ports.