Pre-Authentication Failure with Vista

I've just added a Vista Ultimate system to a W2K network. The machine is
logging the following whenever it's started, logged in, or unlocked:

Event Type: Failure Audit
Event Source: Security
Event Category: Account Logon
Event ID: 675
Date: 3/5/08
Time: 9:40:43 AM
User: NT AUTHORITY\SYSTEM
Computer: DC
Description:
Pre-authentication failed:
User Name: User [or COMPUTER$]
User ID: DOMAIN\User [or DOMAIN\COMPUTER$]
Service Name: krbtgt/DOMAIN
Pre-Authentication Type: 0x0
Failure Code: 0x19
Client Address: x.x.x.x


Searches on Google and MS groups turn up a bunch of similar, unanswered
questions or references to a patch for SBS 2003 (we're on W2K Server). None
of the XP machines have the problem. No events show up for the same user on
non-Vista workstations.

Any suggestions?

Thanks,

--
Yoann Roman