Error Message: Object is not set to an instance of an object (76691)

The random object reference not set to an instance of an object error messages on backups are across all luns, all VMs, and all hosts.

vRanger is installed on the same server as Virtual Center (Strongly not recommended)

Symantec Endpoint Protection 11.x is installed on the vRanger server

On some ocastions, once vRanger server reboots, everything is fine for a day or so and then backups start to fail with the object reference error.

Snacnp.dll driver installed by Symantec EndPoint Protection is causing the backups to fail.

Please uninstall Symantec Endpoint Protection.

Also it would be recommended to move/relocate vRanger installation away from vCenter application as it may cause other errors with vCenter and vRanger.

Unfortunately there is no possible way to re-install vRanger on a separate server and import the database.

This will have to be a new installation of vRanger.

What you can re-import the repository, but the jobs and connections to ESX(i) servers will have to be recreated.