Double check your Win firewall again (humour me).
User Cant Connect - LimeWire

Some people have had problems with 1.6.0_01. Try this version of Java. Use the JRE offline installer & remove your current Java before you install this one.
Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 11

Tiscali are notorious for connection issues. Have you tried connecting outside of peak hours? Check out these threads for more info. Changing ports has worked for some people. Try port 64049, or something in the range of 49152 - 65535.
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

You could also 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.

There's no firewall in your modem, do you also have a router?