Verify that both the public (shared) connection and the private connection are not in a Cable Disconnected state by opening Network Connections in Control Panel. Verify that the public (shared) connection has an IP address.
For more information about common NAT configuration issues, see article 293497 in the Microsoft Knowledge Base (see the following Related Knowledge Base Articles section). If this article does not apply to your situation, review the System event logs for other events that were logged around the same time as this event. In many cases, the same low resource errors or system errors that affect the NAT driver also affect other parts of the system.
Check the available resources on this system by using Performance Monitor. For more information about using Performance Monitor, see article 305610 for Windows XP or article 302521 for Windows 2000 Server or Windows Server 2003 in the Microsoft Knowledge Base (see the following Related Knowledge Base Articles section). For more information about using Task Manager, see Help and Support.