VMware Backup Error: Failed to determine disk areas to backup for VM disk (4033016)

Environment Details:
NetVault Server: 9.1.1 Windows 2008 R2 64Bit
NetVault Client: 9.1.1 Windows 2008 R2 64Bit

VMware Plugin: 2.6.5
ESX Server: ESX 5.1.0 Build 1117900 Enterprise
VDDK: 5.1.1

VMware Plugin backup has the following error messages within the Binary log:

Error 2013/09/17 13:47:31 109 Data Plugin INF-SMARTDISK-2 TaskID 3u Failed to determine disk areas to backup for VM disk '[SAN2_Vol3] SITR-M-GEOSRV-1/SITR-M-GEOSRV-1-000002.vmdk'

With sub text:
Module/Thread Id Code Time Message
VMWSLAVE:02708 114 0 124731 Will use change id '*' to query for changed disk areas
VMWVIM :02708 683 0 124731 Querying for changed disk areas from sector at offset 0 bytes
VMWVIM :02708 686 0 124731 Failed to get changed disk areas: 12
VMWVIM :02708 29 0 124731 Soap error is A specified parameter was not correct.
deviceKey

From the VMware Plugin Trace has the following errors:

0 VMWVIM ??? 2708 686 0 124731881317 Failed to get changed disk areas: 12
0 VMWVIM ??? 2708 29 0 124731881317 Soap error is A specified parameter was not correct.
0 VMWABM ??? 2708 66 0 124731881317 We now have 0 data extents covering 0 bytes
6 VDDK            ???       2708     19        0          124803814572  VDDK: 2013-09-17T14:45:23.487+02:00 [02708 info 'transport'] Disk [SAN2_Vol3] DEV-A-SITR-02/DEV-A-SITR-02-000002.vmdk is marked as independent. Ignoring for backup.

6 VDDK            ???       2708     19        0          124803814572  VDDK: 2013-09-17T14:45:23.487+02:00 [02708 info 'transport'] Disk [SAN2_Vol3] DEV-A-SITR-02/DEV-A-SITR-02_1-000002.vmdk is marked as independent. Ignoring for backup.

6 VDDK            ???       2708     19        0          124803814572  VDDK: 2013-09-17T14:45:23.487+02:00 [02708 info 'transport'] Disk [SAN1_Vol1] INT-A-GAIA-3/INT-A-GAIA-3-000002.vmdk is marked as independent. Ignoring for backup.

6 VDDK            ???       2708     19        0          124803814572  VDDK: 2013-09-17T14:45:23.487+02:00 [02708 info 'transport'] Disk [SAN1_Vol1] INT-A-GAIA-3/INT-A-GAIA-3_1-000002.vmdk is marked as independent. Ignoring for backup.

Unfortunately Independent Disks are not backed up and the VMware 2.6 Plugin Users Guide has been amended to contain some considerations (Bug 21884).

You can find further information within the VMware 2.6 Plugin Users Guide under sections 4.1.1 and 5.2.1 on the following link under the Documentation tab:

https://support.quest.com/NetVault Backup