A computer whose network card with that hardware address is configured to use the IP address as the computer where the error message is being displayed. Chances are that the second computer cannot access the network because the router controlling that subnet can't map two hardware addresses to the same IP address so you may be able to find it by looking for a computer with network problems.
The computer where you are seeing this error and the computer that is causing the problem have two possible configurations for each computer so we have four possible scenarios. ( 00, 01, 10, 11 )
00 - both computers use their hosts file to configure their IP address
01 and 10 - one computer uses DHCP and the other uses its hosts file to configure its IP address
11 - both computers use DHCP to configure their IP address
The 11 scenario is the least likely unless they are using different DHCP servers to obtain their address.
The resolution is to find the problem computer and ensure that it and the computer showing the error message are configured to use different IP addresses.
Last edited by stress_junkie; 05-30-2008 at 08:55 AM.