User Admin Locked Out Every Night

I have one admin that is getting locked out every night. When I look in the logs I see pre-authentication failures for the user. Failure Reason = 0x18. If looked up documentation and I've check that all RDP sessions are closed. Rebuilt her profile on her machine. We turned the PC she works off and the account still locked over night. I see in our logs we get a lot of pre-authentication errors for other users as well. We run 5 2003 Active Directory servers and 1 2008 Active Directory Server. The functional level of the domain is set to 2003.


Service Information:
    Service Name:        krbtgt/


Additional Information:
    Ticket Options:        0x40810010
    Failure Code:        0x18
    Pre-Authentication Type:    2

Certificate Information:
    Certificate Issuer Name:        
    Certificate Serial Number:     
    Certificate Thumbprint:        

Certificate information is only provided if a certificate was used for pre-authentication.

Pre-authentication types, ticket options and failure codes are defined in RFC 4120.

If the ticket was malformed or damaged during transit and could not be decrypted, then many fields in this event might not be present.