This looks like an input/output error when vmPRO was trying to copy the vmdk file from the VM over to target storage.
You could check the VM event logs to see if there is additional information, but to resolve I would attempt to rediscover the VM via vmPRO.
Select the VM from the list of VM via vmPRO GUI, then de-select export and CBT (if enabled), then save. Then select the VM again and enable export and CBT. After this is done, try running the backup again.
I am having the same error. I did what Jerry suggested, but it didn't work. Any other ideas?
Jerry suggested: "Select the VM from the list of VM via vmPRO GUI, then de-select export and CBT (if enabled), then save. Then select the VM again and enable export and CBT. After this is done, try running the backup again."