Can you download and install vBackup version 4.0.1 PR5? In this version we added the ability to test all disks in a backup (from the backups list) in vBackup Client. Simply right-click the backup and click Test Disks. Please reply with the results of the test.
PLEASE NOTE: You do not need to uninstall version 4.0. Just download the version 4.0.1 PR5 zip file from our website and follow the instructions in the included readme.txt.