BACKUP - The login has insufficient authority? (39369)

When user perform backup, it did not have enough privilege, and came back with lack of permission to execute through VDI.

Sample backup script:
exec master.dbo.xp_backup_database @database = mydbname,@filename = \\valid.path.specified.here\mydbname.bak
,@threads = 1, @init = 1, @logging = 1

Msg 62309, Level 19, State 1, Line 1, Sqlstate 01000
SQL Server has returned a failure message to LiteSpeed 2005 which has prevented the operation from succeeding.
The following message is not a LiteSpeed 2005 message. Please refer to SQL Server books online or Microsoft technical support for a solution:

BACKUP DATABASE is terminating abnormally.
The login has insufficient authority. Membership of the sysadmin role is required to use VIRTUAL_DEVICE with BACKUP or RESTORE.

1. Grant SYSADMIN to perform backup for VDI.
a. Open your SQL Server | select instance | select security folder | select account | right click | select server roles | check system administrators.

2. Additional information for VDI security requirement;
Microsoft SQL Server Virtual Backup Device Specification:
Security
The system objects used to implement the virtual device set are secured with an access control list. This list permits access to all processes running under the account used by the primary client. Access is also permitted to processes running under the account used by Microsoft SQL Serverâ?, as recorded in the system services configuration.

The server connection for SQL Server that is used to issue the BACKUP or RESTORE commands must be logged in with the sysadmin fixed server role. For more information, see Microsoft SQL Server Books Online.

Microsoft site: http://msdn2.microsoft.com/en-us/library/bb447591.aspx