Problem:  Windows Updates fails to install on Windows 2008 R2 System Center Data Protection Manager (DPM) server.

Errors:  Specific errors may include, "Installation Failure: Windows failed to install the following update with error 0x80070643".

Solution:  Delete the Windows Update cache and remove all superseded service pack backup components to resolve the issue.  N.B., This situation is not specific to DPM; and can help with other Windows environments, including Windows 8.1 & Windows 2012 R2.

1. Stop the Windows Automatic Update Service from the command line:
   
   net stop wuauserv
2. Go to the Windows directory from the command line:
   
   cd\windows
3. Purge the update cache from the command line:
   
   rd /s SoftwareDistribution
4. Start the Windows Automitic Update Service from the command line:
   
   net stop wuauserv
5. Remove superseded cumulative Service Pack backup components:
   
   Dism.exe /online /Cleanup-Image /SPSuperseded

That's it.


References:

http://technet.microsoft.com/en-us/library/dn251565.aspx
http://support.microsoft.com/Default.aspx?kbid=971058

DPM Network Administration Windows