I have an Exchange 2007 running on a Windows 2008 server that is my DC. In the last 2 weeks the system has stopped functioning twice and each time required a Hard powerdown. the last error in the log is a Event Code1006 error code85 "The processing of Group Policy failed. Windows could not authenticate to the Active Directory service on a domain controller. (LDAP Bind function call failed). Look in the details tab for error code and description." Is this the cause or just a reaction the system locking up? Any clues as to the reason why this is happening?