Plugin-ul VMware 2.6 nu asigura inca suport pentru vddk 5.5:
Thank you for contacting Dell Software (formerly Quest). I have taken ownership of your Service Request Number 2325798 - Netvault backup of virtual machine on vsphere 5.5 failed.
Vmware has made changes to the VDDK 5.5 so this is not simply a compatiblity issue, from what I understand we would be looking at supporting the 5.5 vddk some point in Q2 next year, this has been logged in our system under the ID 23460.
I know this is not what you want to hear at the moment, but this is currently the status on the release.
Until then we will need to operat within the supported ESXi which is vddk 5.1
as per our support matrix you can see that the vddk 5.5 is currently not supported: