I went to install the AD Management Gateway Service (KB968934) on a Domain Controller running Windows Server 2008 SP2 and I received the error shown below.
Installer encountered an error: 0x80070422. The service cannot be started, either because it is disabled or because it has not enabled devices associated with it.
The problem was that the Windows Update service had been set to Disabled by Group Policy on the DC. After enabling the service (temporarily) the msu package installed ok.
Kind of obvious really, but it had me guessing for a while.