First thing to try: 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.

Just for now, stick with the Java 1.5.0_11. Remove any other Java versions that you have installed.

Try port forwarding for your router, the instructions are here.
Port Forwarding for the Linksys WRT54GS
Don't forget the step of setting up a static IP address first (or port forwarding won't work). LW's lilstening port, port in the 'manual port forward' box & port forwarded within the router all have to be the same number