Do you know for sure that they're blocking p2p?
Do this test & see what result you get (click on link)
http://www3.limewire.com:6346
If you know that your ISP's definitely blocking p2p, you could try changing ports. There's no guarantee it'll work but it's worth a try! Follow the advice here.
Alternative Ports

Have you read this sticky & made sure that your own software firewall's configured?
Connection problems? Check here first!


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