Virtual Machine backup using AVVI Agent (Agent for VMWare Virtual Infrastructure) fails with error "V-79-57344-65304 - The Virtual Machine resource is not responding. Backup set canceled".
Long list of "Map disk region" messages can be seen in Vcenter events.
The 'Map Disk Region' messages can occur if there are old snapshots on the virtual machines.
This could be a result of an old left over snapshot in snapshot manager. Delete these old snapshots by accessing the virtual machine though vSphere Client or vCentre as this may help resolve this issue.
Backup Exec 2010 R3