Windows Server 2008 R2 Service Pack 1 fails with 800F0818

I was recently attempting to run Windows Server 2008 R2 Service Pack 1, which would fail with the error code 800F0818 due to Windows Update corruption.

In order to resolve the issue, run the System Update Readiness tool and then install the service pack.

The System Update Readiness tool is available from http://support.microsoft.com/kb/947821.