You install several Updates. After the successful installation, you notice you cannot add or remove features/roles in the Server Manager

After receiving this error i first installed the System Update Readiness Tool for Windows Server 2008 R2 x64 Edition (KB947821) [February 2011] which i hoped would give me an indication of the issue.
After installing the above check the following log “%systemroot%\Logs\CBS\CheckSur.log”.
After downloading the MSU i extracted what was in the MSU with the following command
Expand -F:* Updatename.msu C:\FolderLocation
This then extracted a CAB file which i then in return ran another expand command against
Expand -F:* cabname.CAB C:\CabDestination
Once the files from the CAB file have expanded run a search for the Unavailable repair files mentioned earlier
  • Package_for_KB2454826_RTM~31bf3856ad364e35~amd64~~6.1.2.0.cat
  • Package_for_KB2454826_RTM~31bf3856ad364e35~amd64~~6.1.2.0.mum
Once you have found the above 2 files copy and paste them to the “%systemroot%\Servicing\Packages” if prompted to overwrite then do so.

http://blogs.technet.com/b/roplatforms/archive/2010/05/12/how-to-fix-server-manager-errors-after-installing-updates-hresult-0x800f0818-hresult-0x800b0100.aspx