You tell us. Can you give us a total desciption of your set up: 1. OS version, 2. What firewalls you have, 3. ram, 4. HDD space available, 5. Connection type, 6. Modem & router brand name & model numbers, 7. Where are you trying to connect from (home, school, work, etc.)?
These details are vital if you want us to find out what your connection problem is.

What you can try in the meantime is 1. Update your Java: Java 1.4.2 (click on link)

2. Delete your LW preferences folder called .limewire & found here (whilst LW is closed!):
C:/Documents And Settings/your_username/.limewire for Windows users.