In Web Client the following message shows up:
Illegal Operation attempted on a registry key that has been marked for deletion

The error message is thrown by IIS. After restarting IIS the message should not occur anymore.

If the message reoccurs, you can change following group policy:

  1. Open the group policy editor (gpedit.msc)
  2. Go to Computer Configuration -> Administrative Templates -> System -> UserProfiles -> Do not forcefully unload the user registry at user logoff.
  3. Change the setting from “Not Configured” to “Enabled”