See if this is any help
FAQ
http://www.limewire.com/index.jsp/faqs#pla2
Taken from the above link..this is the section you need
Q: I have LimeWire open but I can't seem to connect. I know I have an internet connection so what's going on?
A: Your ISP (AOL, Cablevision, etc....) might be blocking Gnutella traffic. For example, the ISP STARBAND blocks all Gnutella activity at their network. If you're on Windows, perform this test to see if you can connect to Gnutella. Non-Windows users can run this as well if they know where to find the telnet program.
1. From the Start menu, choose "Run".
2. In the resulting dialog box, type "telnet 64.61.25.171 6346". Click OK.
3. A window will pop up. If it doesn't say "GNUTELLA OK" within a few seconds, your ISP is probably blocking Gnutella traffic. In this case, there's not much we can do. Non-Windows users can run this as well if they know where to find the telnet program.