Talk Talk are probably a big part of your problem

http://www.gnutellaforums.com/downlo...downloads.html
ISPs that throttle p2p - The Scream!
Is that it then, TalkTalk

Do you know if your modem's just a straight modem, or whether it's a modem/router? Most routers & modem/routers have an internal firewall. Without a model number & brand (apart from talk talk), it's a bit hard to know. If you want to try getting rid of the firewall icon: If your modem supports UPnP, enable it & use the UPnP option within Limewire's tools > options > advanced > firewall config. If that doesn't work then go here to the port forward site here.
PortForward.com - Free Help Setting up Your Router or Firewall

See if you can find your router in the list. If you can, you'll find step by step instructions for port forwarding for your modem/router. Follow the instructions & don't forget the step of setting up a static IP address if that's included