Missing Outlook Profiles

We have several thin client users that have their Outlook profile missing when they logon to TS.  When they start Outlook, it acts like they have never had their profile created, even though it was working fine the previous day.  This is occuring with two different TS 2008 servers.  I checked the registry, and the Outlook profile keys are not there.  There are no events logged on the server, and no any other errors.  Re-creating the Outlook profile works fine.  There is no other part of their profile (desktop shortcuts, favorites, etc.) that is missing or otherwise not functioning correctly.  I do not see any pattern linking the small number of users impacted so far.

Any suggestions?