So did you configure the XP Firewall?

If it was working 3 months ago & suddenly stopped working & deleting the LW preferences folder didn't work then it looks like your ISP Provider has put filters in place to stop you using p2p programs. This is becoming more frequent nowadays as isp's deal with heavy net traffic.

Suggestions:
1. try a different port for LW. Go to LW's menu Tools>Options>Advanced>Firewalls & change the listening port to 80 & press apply. Then close LW & re-open.

2. Try a proxy:
A Fix for those whose ISP's block Limewire pages 1 & 2 which has a link to alternative instructions.

Another Insight proxy solution

http proxies

A Successful http Proxy Solution