On Windows Server 2008 R2 I am getting a DCOM event error 10009 "DCOM was unable to communicate with computer X" I can't ping computer X, I don't know what computer X is, and computer X is not in AD. What can I do to either fix this or make it so the events are not logged.
WMI uses DCOM underneath, so if you have any scripts or monitoring that uses WMI, those scripts could be misconfigured and trying to contact the unknown server.
The answer is still partially unknown. The best I could figure out was that there is a printer or thin client on the network that isn't on the domain.
It could be that computer X is trying to communicate with your server, but the communication fails and the event gets logged on the server too; having the event there doesn't necessarily mean the server itself initiated the connection.
About what it could be... well, practically anything. DCOM is the underlying protocol for almost anything that Windows does on the network and is not plain file sharing.
If you can't resolve the host name of computer X to an IP address and don't have any other way to fint it, then your only option is using a network sniffer on the server to see where the traffic is coming from.