Recently while troubleshooting a LAN that had both an internet outage as well as a general network outage, it was discovered that the "IP Address Translation" driver was the culprit.

All signs pointed to the Windows Firewall (or some third party firewall) as the item which was preventing network traffic from reaching its destination. It was not until the IP Address Translation "Non-Plug and Play" driver was disabled that the network was back up and functioning.

IP Address Translation is a synonym for Network Address Translation (NAT), which is commonly performed by a router or firewall. It is for this reason that the driver was disabled, and it is still unclear how the driver became activated in the first place, since it was on a Windows 2003 server with no (known) user intervention at the console for several months.