This error may occur in ArcCatalog when granting or revoking privileges on objects in the geodatabase:
One of the objects in question has either a custom object or custom class extension associated with it. The class extension or DLL for the custom object is not registered on the machine where the privileges are being modified.
Warning: The instructions below include making changes to essential parts of your operating system. It is recommended that you backup your operating system and files, including the registry, before proceeding. Consult with a qualified computer systems professional, if necessary. Esri cannot guarantee results from incorrect modifications while following these instructions; therefore, use caution and proceed at your own risk.