Need more info. Best guess is a firewall.
1. what OS version? (eg: Windows 98, XP,OSX, Vista)
2. What firewalls you have ?
3. How much ram ?
4. Hard Disk space available ?
5. Connection type (eg: dialup, broadband, cable, etc.) ?
6. Modem & router brand name & model numbers ?
7. Where are you trying to connect from (house, appartment complex, school, student accomodation, work, etc.) ?
8. What version,LimeWire & Java,Go to L/W's Help/About L/W, THIS show both LW & Java version.?
9. Who is your ISP provider (Internet Service Provider) ?
10. Do this test click here:
http://www3.limewire.com:6346/ should say 'Your test worked!. What happens ?
11. Are you sharing the connection with other computers or p2p sharing programs? If yes, please give details of set up.
12. Is this a your 1st try at LW or is this a new problem with an experienced user.?
13. Do you see a brick wall in front of the blue world icon at the bottom of LW's interface ?
14. Have you given full permisions for LimeWire to pass through your Firewall ?
15. XP users, Please state XP firewall on or off.?