I have been using my Windows Server 2008 R2 Active Directory Domain Controllers as backup Agent Handlers - since upgrading the AH to release 5.1.2 and MA to 5.0.1, I have a very serious issue in which these systems have macmnsvc running at 100%.
This seems to only affect the Domain Controllers -- Other 5.1.2 AH are fine, and other systems running only MA 5.0.1 are fine as well.
This repeats until the system is rebooted. After that, things are normal for awhile -- then at some unknown point, the system will go back to 100% utilization. The process cannot be stopped due (I assume) to the McAfee self-protection system.