Windows 2008 R2
DCOM was unable to communicate with the computer <servername> using any of the configured protocols.
Windows 2003 R2
A DPM agent failed to communicate with the DPM service on <servername>because of a communication error. Make sure that <servername> is remotely accessible from the computer running the DPM agent. If a firewall is enabled on <servername>, make sure that it is not blocking requests from the computer running the DPM agent (Error code: 0x800706ba, full name: <servername>). 
DPM Server Warning
The DPM protection agent on <servername> could not be contacted. Subsequent protection activities for this computer may fail if the connection is not established. The attempted contact failed for the following reason: (ID 3122)
The protection agent operation on <servername> failed because the service did not respond. (ID 316 Details: Internal error code: 0x8099090E)
Solution:
On the Workgroup Server
SetDpmServer.exe –dpmservername <servername> -isnondomainserver –username <dpmuseraccount> –productionserverdnssuffix <fqdn>
On the DPM Server
Attach-NonDomainServer.ps1 –dpmservername <servername> –PSName <servername> –UserName <dpmuseraccount>
Don’t forget to set Password never Expires on the DPM User account