Make sure that your Norton firewall's configured to allow LW.
PortForward.com - Free Help Setting up Your Router or Firewall

Tiscali might be part of the problem!! Lots of customers have had connection problems. Have a read of these threads. You could try changing ports...in LW tools > options > advanced > firewall config. Change LW's listening port to 64049 (or something in the range of 49152 - 65535) > Apply > ok.

I have found a solution to getting Limewire to work with Tiscali
Tiscali blocking Limewire
can't connect between 5pm-11pm
Tiscali & Limewire
Connection Problem - with Tiscali.co.uk


Try port forwarding for your router, the instructions are here. Don't forget to set up a static IP address first. LW's listening port, port in the 'manual port forward' box & port forwarded within a router must all be the same number
Port Forwarding for the Thomson/Alcatel SpeedTouch 510