Who is your ISP? If it's Optimum Online, there are lots of other people in the same boat with you.

If you're not with OO, tell us 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

Do this port test & see what result you get
http://www3.limewire.com:6346

Make sure your firewall's configured as per the sticky at the top of this section