Read this
Connection problems? Check here first!

Make sure that you're only running 1 firewall & that it's configured for LW.
Do this test & see what result you get
http://www3.limewire.com:6346

Read all the info about UPnP & internal firewalls within modems/routers... does any of it apply to your modem or router? If nothing helps, post back with your details

OS(Win XP etc)
LW & Java version (help > about LW & you'll see)
Firewall you're using
Modem/router brand & model
ISP
Connection type (DSL etc)
Where you connect from (home, school etc)
Are you sharing a connection with other computers
Is this your first try with LW