Kerberos Error for Farm Account

Hello

I keep seeing the following Kerberos error on my WFE every minute and I'm not sure why it is targeting the FARM account.

A Kerberos error message was received:
 on logon session
 Client Time:
 Server Time: 22:34:35.0000 11/20/2013 Z
 Error Code: 0x1b Unknown Error
 Extended Error:
 Client Realm:
 Client Name:
 Server Realm: Domain.INTERNAL
 Server Name: svc-spfarm
 Target Name: svc-spfarm@Domain.INTERNAL
 Error Text:
 File: 9
 Line: 12be
 Error Data is in record data.

I have not set a SPN for the Farm account, so I'm not sure what is causing it.

Thanks for any suggestions.

Yoshi