We also (and a lot of other end users) have this problem on Windows 7 and Windows Server 2008 R2.
When we disable the Enable behavior monitoring in the settings of SCEP and
reboot the computer/server the errors don't appear anymore in the event viewer.
It seems that SCEP blocks the registry settings/values of the following keys:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\MsMpSvc\Start
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\MsMpSvc\FailureActions
I verified this in the following log file of clients with the issue:
C:\ProgramData\Microsoft\Microsoft Antimalware\Support\MPLog-xxxxx20xx-xxxxx.log
These log contains the following entries:
TelemetryName:Behavior:Win32/MpTamperBlockSrv.E
TelemetryName:Behavior:Win32/MpTamperBlockSrv.D
So it seems that it is SCEP itself which is preventing changes to the registry keys which it needs to change.
I noticed that this behaviour started with the update of the engine from version 1.1.11502.0 to version 1.1.11602.