Hi We are actually upgrading our servers from Vsphere 4.1 to 5.1 First step was to upgrade Vcenter Server. We created a new one with same name and same IP Address. It worked like a charm form VMware part, and we are able to manager our 4.1 hosts. But in Backup Exec, backups do not work well anymore. At first, they were failing because VMs were not selected anymore in backup jobs. I selected VMs again for each backup job and backup do start again. It create snapshot, backup Vm and suppress snapshot correctly. But job fail with this kind of error. VMTools were not upgraded in Vms and VMware Hosts still are in 4.1. Only Vcenter was upgraded right now. Agents are in VM BackupExec server is 2012 SP3. Agents are not all SP3, but it is failing too for all jobs even if Agent version is the last one Backup-
BackupV-79-57344-38260 - Unable to create a snapshot of the virtual machine. The virtual machine may be too busy to quiesce to take the snapshot.
Verify- SRV-BACKUP02Unable to attach to VMVCB::\\srv-vcenter01.feuillatte.com\VCGuestVm\(DC)CVCNF(DC)\vm\SRV-SPACEMAN.
V-79-57344-33899 - The resource could not be backed up because an error occurred while connecting to the Agent for Windows. The correct version of the Agent for Windows must be running on the target computer.
A selection on device VMVCB::\\srv-vcenter01.feuillatte.com\VCGuestVm\(DC)CVCNF(DC)\vm\Machine virtuelle détectée\SRV-SPACEMAN was skipped because of previous errors with the job.
I already took a look at this article, but nothing there does apply as Vmware tools were not upgraded.
Problem happen on all Vm's, so it is not related to overloaded system or unsupported OS and so on
...matter of interest, but have you tried to revert back to the old VC and then run the jobs again?
Wonder if it isn't the way that BE might be interpreting these VMs being hosted on ESX 4.1 while the VC is on another version...?