Could not create LookupUserWrapper. Cause: This is an unexpected error. If it happens even after following the resolution ...

Could not create LookupUserWrapper.

Cause: This is an unexpected error. If it happens even after following the resolution steps, please contact product support.
Resolution:
Shutdown IIS and ensure that no ASP.Net worker process are running. Re-start IIS.  If problem persists, try re-starting the machine.