According to the System Center Configuration Manager Team Blog, if Windows hotfix KB974571 is installed on a Windows 7 reference image, then it is highly likely that you would see the following log entries in smsts.log when deploying this image to an existing client. Notice that because the client certificates were not found, the end result is that the client uses a new certificate to register itself, losing its own identity in the process.

Installing SMS client
Clearing existing client configuration.
Cleaning existing client certificates from SMS certificate store
Restoring SMS client identity.
The client certificates were not found. New certificates will be generated.
Successfully restored the client identity.

They have all the details, including a couple workarounds here.

J.C. Hornbeck | System Center Knowledge Engineer

The App-V Team blog: http://blogs.technet.com/appv/
The WSUS Support Team blog: http://blogs.technet.com/sus/
The SCMDM Support Team blog: http://blogs.technet.com/mdm/
The ConfigMgr Support Team blog: http://blogs.technet.com/configurationmgr/
The SCOM 2007 Support Team blog: http://blogs.technet.com/operationsmgr/
The SCVMM Team blog: http://blogs.technet.com/scvmm/
The MED-V Team blog: http://blogs.technet.com/medv/
The DPM Team blog: http://blogs.technet.com/dpm/
The OOB Support Team blog: http://blogs.technet.com/oob/
The Opalis Team blog: http://blogs.technet.com/opalis
The Service Manager Team blog: http: http://blogs.technet.com/b/servicemanager
The AVIcode Team blog: http: http://blogs.technet.com/b/avicode