Try deleting your LW preferences found here:
OS X: /Users/your_username/Library/Preferences/LimeWire
Windows: C:/Documents And Settings/your_username/.limewire
Linux: ~/.limewire

And delete the folder called .limewire
It will mean you'll need to reset your LW settings so make a note of them 1st.

What Operating System (OS) version do you use? Which version of LW? What modem & router type? Where are you connecting from (home, school, work, etc.)?