Look at the types.cf located at C:\Program Files\Veritas\Cluster Server\conf\config, the MountV type is most probably missing the "BlockMountPointAccess" attribute.
Issue a hastop -all -force
Take a backup of the existing types.cf file.
STS Veritas Storage Foundation 5.1 for Windows
STS Symantec NetBackup 7.5 for UNIX
STS Symantec NetBackup 7.5 for Windows