Backup jobs that specify only the Hotadd transport mode will fail if a virtual machine is backed up from a VMware vSphere 5.5 environment.
V-79-57344-38371 - The Hotadd transport mode is not supported in this version of VMware vSphere
This issue may occur due to vSphere not able to open the disk. The Virtual Disk Development Kit (VDDK) 5.1 U1 does not work on vSphere 5.5 and VMware is aware of the issue.
Note: VMware vSphere 5.5 support has been added in Backup Exec 2012 Service Pack 3. Backup Exec 2012 Service Pack 3 and Service Pack 4 use the VDDK 5.1 U1.
As described in the following VMware documents, the VDDK 5.1 U2 is required for HotAdd transport mode to be used against vSphere 5.5.
VDDK 5.1.2 Release Notes
The VDDK 5.1 U2 is used in Backup Exec 2014, so this issue doesn't occur in Backup Exec 2014.
This issue is resolved in Backup Exec 2014 or later versions.
To resolve this issue and receive the new Backup Exec improvements please upgrade to the current version of Backup Exec.
NOTE: Symantec continues to focus on the current release and future releases, there are no plans to address this issue by way of a patch or hotfix in earlier versions of the software at the present time. Please contact your Symantec Sales representative or the Symantec Partner for upgrade information including upgrade eligibility to the release containing the resolution for this issue. For information on how to contact Symantec Sales, please see http://www.symantec.com
WORKAROUND (Backup Exec 2012)
These is no workaround to allow the use of Hotadd transport mode. The only workaround available in Backup Exec 2012 is to specify a different transport mode that is supported by your environment in the virtual machine settings of the backup job.