Make sure that the Windows firewall is off & that Norton firewall is configured properly.
PortForward.com - Free Help Setting up Your Router or Firewall

Try port forwarding for your router. The instructions are here.
Port Forwarding for the Siemens 4200
Don't forget the step of setting up a staric IP address first. LW's listening port, port in the 'manual port forward' box & LW's listening port all have to be the same number

Is there any chance that you've exceeded your monthly download limit? If you have, you'll probably be shaped back to snail speed & so your downloads will be slow!