When you try to start the Microsoft Exchange Service Host service on a Microsoft Exchange Server 2010 server, the service crashes and the following event is logged in the Application log:
Additionally, the following event is logged in the System log:
This issue occurs because the Exchange Service Host service encounters a System.NullReferenceException exception when the service tries to access the system access control list (SACL) during the startup process.
To resolve this issue, install the following update rollup:
2746164 Description of Update Rollup 6 for Exchange Server 2010 Service Pack 2
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.