I've been geeting Event ID 675 errors on my DC's lately. The accounts referenced are the machine accounts of my Exchange servers. The error is as follows- Event Type: Failure Audit Event Source: Security Event Category: Account Logon Event ID: 675 Date: 12/2/2005 Time: 3:58:39 PM User: NT AUTHORITY\SYSTEM Computer: OPNYC10 Description: Pre-authentication failed: User Name: EXNYC02$ User ID: OPANDCO\EXNYC02$ Service Name: krbtgt/OPANDCO.COM Pre-Authentication Type: 0x2 Failure Code: 0x18 Client Address: 10.225.53.27 For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. I can't really find anything applicable at Eventid.net. Thanks