Make sure that LW's being allowed through the Windows firewall.
User Cant Connect - LimeWire

Try reinstalling Java (just in case that's somehow become corrupted). Java SE Downloads
Or try this older version, which has worked well for lots of people: Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 11
Whichever Java version you use, download the JRE offline installer & remove any other Java versions before installing another one.

Next, 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 change 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 get stuck with deleting the prefs folder, have a look at this post points 1 - 6.
http://www.gnutellaforums.com/connec...tml#post296950

If LW still won't connect, within LW click on File > disconnect. Wait 5 minutes then File > connect.

If you can find your router on the list here, try port forwarding.
PortForward.com - Free Help Setting up Your Router or Firewall
Don't forget the step of setting up a static IP address, if that's part of the instructions. LW's listening port, port in the 'manual port forward' box & port forwarded within the router setup should all be the same number.

If it still won't connect, there's another fix to try here (also explained in that thread I linked to with points 1 - 6).
http://www.gnutellaforums.com/connec...t-fix-try.html