First of all, delete LW's preferences folder when LW's properly closed. See point 3 here & also point 2 if you've used older versions of LW in the past (there could be a folder in either location).
Fixes for LimeWire
This will kill all of your settings within options, you'll have to go back through afterwards & reset things. If you're not sure of your settings, go through LW's tools > options & write them all down, so that you can reset things later.

If you've recently updated Java, some people have had problems with Java 6 update 1...use the latest Java 6 update 2. Use the JRE offline installer & remove your old Java version(s) before you install this one.
Java SE Downloads

If that Java is no help, try this older version. Same deal with the JRE offline installer & removing other Java versions
Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 11

Try port forwarding for your router. The instructions are here.
Port Forwarding for the Westell Versalink 327W
LW's listening port, port in the 'manual port forward' box & port forwarded within the router all have to be the same number.

This has worked for some people.
General Connection problems