You said in your first post that you have turned off Norton and McAfee firewalls, do you have all of these firewalls installed on your computer...
What protection are you using, not having any Antivirus protection is not a good idea especially if you want to use Limewire...
When you turned off your routers Nat Firewall did you use the port forwarding instructions and set your port numbers correctly ??
Port Forwarding for the Motorola WR850G