Tiscali are a pain, so many people are having probs with them lately.

Double check the config of your XP firewall
Firewall setup

Some people have found changing ports helps. To do this, in LW go tools > options > advanced > firewall config. There you can change LW's listening port. Good ones to try are 49152 - 65535. Someone recently got connected after weeks of pain using port 139. Have a read of these...

Tiscali & Limewire
can't connect between 5pm-11pm
I have found a solution to getting Limewire to work with Tiscali

You could also see whether Java 1.6 makes any difference (it did for one person). Use the JRE offline installer here & remove your old Java versions before installing the new one.
http://java.sun.com/javase/downloads/index.jsp

If you find that you do eventually connect, try to find the brand & model of your router (might be written underneath) & we can try to get rid of that firewall icon