UserEnv experienced an error applying Group Policy to the domain controller. Group Policy must be applied successfully for domain controllers to function properly because domain controllers get several critical permissions, such as Access this computer from network, through policy.
Because of the architecture of UserEnv, Microsoft Operations Manager (MOM) is unable to directly report the specific problem.
Windows did not apply extension %1 because the registry extension failed.
To enable UserEnv logging, see Knowledge Base article 221833, “How to Enable User Environment Debug Logging in Retail Builds of Windows,” at http://go.microsoft.com/fwlink/?LinkId=25636. The log file provides details for the specific error.
Microsoft Help and Support for Microsoft Windows Server 2008 and above
Microsoft Knowledge Base