I was deploying Windows ThinPC using MDT with a customer, and received this error:
Windows could not parse or process unattend answer file [C:\MININT\unattend.xml] for pass [windowsPE]. A component or setting specified in the answer file does not exist.
According to the MS forums this should be solved in MDT 2012 beta 1. So we upgraded to MDT 2012 beta 2, but unfortunately the error remains.
Deleting the <UpgradeData> node from the unattend.xml, like Michael mentioned, fixed the issue. Windows ThinPC deployed successful when this node was removed.