Summary:  This solution is a gem for the unlucky folks still running DPM 2010.  Windows 2012 R2 innovations resolve many performance problems associated with DPM 2010:

• Improved Networking 
• Improved Storage 
• Improved iSCSI
• Fixes VSS Orphan Issues
• Fixes Volume Enumeration Issues
• Fixes DPM Startup Hangs

Problem:  DPM 2010 is not supported on Windows Server 2012.  This is an unsupported.  DPM client agents get DCOM errors in this unsupported configuration.

Solution:

1. Install Windows 2012R2
2. Install DPM 2010
3. Unjoin Domain.  Ensure Computer Object is not in AD.
4. Rejoin DPM server to domain.
5. Add DPM server to the Distributed COM Users AD group.
6. Manually add DPM agents.

References:

http://serverfault.com/questions/563088/dpm2010-windows-2012-dcom-errors-communicating-with-all-agents

DPM