Failure Audit when connecting to TFS

Hi,

we use TeamCity together with TeamFoundationServer. TeamCity connects to TFS, using an AD-User, every 60 seconds to check for changes.
Although the connections work, we get failure-audits on our domain-server:

Event Type:    Failure Audit
Event Source:    Security
Event Category:    Account Logon
Event ID:    675
Date:        11.08.2009
Time:        07:36:16
User:        NT AUTHORITY\SYSTEM
Computer:    <SERVERNAME>
Description:
Pre-authentication failed:
     User Name:    <USERNAME>
     User ID:        <DOMAIN>\<USERNAME>
     Service Name:    krbtgt/<DOMAIN>
     Pre-Authentication Type:    0x0
     Failure Code:    0x19
     Client Address:    <IPADDRESS>

You can work around this issue by turning off the kerberos pre-authentication, but that's not the best solution.
Is there a possibility to fix this issue? Has anyone else expirienced this behavior?

Cheers,
Rainier