Event ID 64 - Certificate thumbrint is nowhere to be found

I have a strange issue with an Event ID 64. Source is CertificateServicesClient-AutoEnrollment. Every 8 hours an error gets logged saying "Certificate for local system with Thumbprint XXXXXXX about to expire or already expired". I've looked through my certs and not one of them matches this thumbprint. I found posts pointing to this article: http://technet.microsoft.com/en-us/library/cc774595%28WS.10%29.aspx but again, none of the certs on this machine match the footprint.

Any ideas are welcome.