Can't Connect With The New PRO Version
 

1. OS version? Windows XP SP2 Home Edition
2. What firewalls you have? XP and Symantec as virus protect
3. How much ram? 1.25 gigs
4. Hard Disk space available? 50GB
5. Connection type? Broadband/Cable Comcast
6. Modem & router brand name & model numbers? Motorola cable modem-Linksys router
7. Where are you trying to connect ? From Home
8. What version of LimeWire (LW) & Java do you have? 4.12.15/ 1.6 Java
9. Who is your ISP (Internet Service Provider)? Comcast High Speed
10. Do this simple test for us. Using your browser go here: http://www3.limewire.com:6346/ The page should say 'Your test worked!'. What happens when you go there? It says your test worked.
11. Are you sharing the connection with other computers or p2p sharing programs? If yes, please give details of set up. No
12. Is this a your 1st try at LW or is this a new problem with an experienced user. New problem after purchasing Pro
13. Do you see a brick wall in front of the blue world icon at the bottom of LW's interface? Yes.
14. For those using a modem/router, how is your modem/router set up...are you port forwarding or is UPnP enabled? UPnP enabled and tried port forward to 25000, no luck.
15. What security programs are you using (antivirus etc)? Some people might not be aware that their security suite includes a firewall. Symantec
16. What country are you living in? Sometimes there are ISPs with the same name in more than one country (eg Clearwire in the USA & also in Ireland). USA
Stuck on "Starting Connection", No connections on connections tab.

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

Birdy's Preference Folder Trick Worked
 

Thanks! I didn't need to change my JRE Version.

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 (http://www.gnutellaforums.com/windows/36420-fixes-limewire-when-lw-isnt-operating-should.html)
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.