Toucan...ouch Use Google to search for Toucan p2p...you'll find heaps of info.
A few things to try, no guarantees though as there's a good chance your ISP is at fault here.

If you have a McAfee firewall, make sure that the XP firewall is off & the McAfee's configured to allow LW.
Port Forwarding for the McAfee Security Center

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


Toucan resell Tiscali & heaps of people who use Tiscali (& Toucan) have had problems connecting/downloading. Have you tried connecting outside of peak hours (6pm - 11pm)? Read through some of these threads, try the fixes...changing ports has worked for a few people.
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 try deleting 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 like, you can try port forwarding to get rid of the firewall icon. The instructions for your router are here.
Port Forwarding for the Netgear DG834G
Don't forget the step of setting up a static IP address first. LW's listening port, port in the 'manual port forward' box & port forwarded within the router all have to be the same number.