Netlogon Service Does Not Start After Applying SP4

MORE INFORMATION

When the Netlogon service tries to add itself to the Administrator's group to start up, it hits a condition that keeps the Netlogon service from starting. This occurs on the first restart after applying SP4. Although the security accounts manager (SAM) is apparently upgraded to its new format, the condition described above prevents the upgrade from taking place, rendering all further access to the SAM impossible. De-installing Service Pack 4, even when it preserves SAMSRV.DLL, does not fix the problem since the SAM itself has not been upgraded properly.