V-79-57344-38277 - Öffnen eines Datenträgers des virtuellen Computers nicht möglich.

I get the above error message when trying to backup several VMs.

The error comes fro the first VM (only?)

BE Vmware agent is licensed and the VMWare Storage API seems to be licensed correctly also.

Is there anything else to be considered ?

I am using BE 2010R3 with all availables hotfixes applied