Security must be initialised before any interfaces are marshalled or unmarshalled. It cannot be changed once initialized. (CoInitialzeSecurity).
Backup of Exchange using 32bit DS-Client (Windows 2008 SP2, Windows 7, Windows 8 or Windows 10). This happened after applying hotfix#5 (13.3)
Suggest to use 64bit DS-Client.
Starting with v.184.108.40.206, only Windows DS-Client 64bit supports Exchange backups"