Have you tried to reset the Computer-Account in the Active Directory?
You can try this or you can delete and precreate an Computer-Account in AD with the same name. After that you have to terminate cifs on your Netapp and rerun the cifs-setup. This will cause al little downtime for cifs-Users, so think about the time you do this.
This helped me with this error shown in the Eventlog of the DC.