getting kind of a weird one WI5.1 with two sites on it - both direct - one has smartcard pass-through for authentication method, the other has smartcard (NOT passthrough) - I can logon to both just fine with my neutered user account. Have a user who can logon to the one with passthrough just fine, but he gets "An authentication error has occurred."a when logging on to the one without passthrough. What does the security log show? why logon successful of course. Event Type: Success Audit Event Source: Security Event Category: Logon/Logoff Event ID: 540 Date: 6/3/2009 Time: 8:29:13 AM User: MyDomain\JoeUser Computer: My_WI_Server Description: Successful Network Logon: User Name: JoeUser Domain: MyDomain Logon ID: (0x0,0x54E4596) Logon Type: 3 Logon Process: Schannel Authentication Package: Kerberos Workstation Name: My_WI_Server Logon GUID: - Caller User Name: My_WI_Server$ Caller Domain: MyDomain Caller Logon ID: (0x0,0x3E7) Caller Process ID: 500 Transited Services: - Source Network Address: - Source Port: - For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. Any clues or wild-a$$ guesses?