Cannot install Exchange agents:"GetWMIComputerSystemType Error: -2147024891 - Access is denied." (4271668)

Installation of Exchange agents (Mail Source Agent, Mail Target Agent, Public Folder Source Agent, etc) on a server fails and you receive an "Access is denied" error message.  The following error is also logged in the emwmigration.log file:

"aeEMWGUIShared::aeEMWGUIShared::modMain::GetWMIComputerSystemType Error: -2147024891 - Access is denied. (Server: SERVERNAME. Username: domain\username)"

The service account (specified in the above message) has the required permissions.  What is causing this error?

This error may occur if DCOM is disabled on the server.

Please ensure that DCOM is enabled on each Exchange server involved in a synchronization job.