Vista event id 675 pre-authentication type 0x0 faliure code 0x19

I am getting dozens of entries like these in the security log on a Windows
2003 DC with SP2 installed. The great majority of these errors are from a
Vista machine and a user on the Vista machine (me), but not all of there are.


However, they seemed to start appearing when the Vista machine joined the
network. In addition, when a Vista-equipped laptop comes to my site from
another one on the domain, the number of these errors increase. Except for
the clutter in the security log, these don't seem to hurt anything.,

I've been looking for some answer (besides, "no user action required") for
some time now and the only cogent answer relates to Vista in a Windowes 2003
SBS environmnet, which mine is not.

Thanks for any help you can give me.
__________________________________________________ _______________
Pre-authentication failed:
User Name: PCXXX$
User ID: NOVUM\TV1186$
Service Name: krbtgt/NOVUM
Pre-Authentication Type: 0x0
Failure Code: 0x19
Client Address: 192.168.2.75
__________________________________________________ _______________
Pre-authentication failed:
User Name: User1
User ID: domain1\User1
Service Name: krbtgt/domain1
Pre-Authentication Type: 0x0
Failure Code: 0x19
Client Address: 192.168.2.75
__________________________________________________ _______________