Providing that your Norton AV doesn't include a firewall , make sure that the XP firewall's allowing LW.
User Cant Connect - LimeWire

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. If that's what you're using, try 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

Have a look here for instructions for port forwarding your Linksys router. find your router from the list, then choose LW from the list of programs.
PortForward.com - Free Help Setting up Your Router or Firewall
Don't forget the step of setting up a static IP address first, if it's included in the instructions. LW's listening port, port in the 'manual port forward' box & port forwarded within the router all have to be the same number

If none of those help, try this.
General Connection problems