Hi Bob,
You mention you have the latest Sony drivers installed.
I would recommend stopping the BE services, and then ensure you can perform a test backup with ntbackup.
If this works, leave the services disabled, and have a go at running tapeinst.exe. Ensure you tick the "use plug and play drivers" box when doing so.
If that still fails, you don't actually need the Veritas drivers- indeed, often they cause issues.
Simply start the BE services, leave your OEM driver installed, open Veritas and run the "Device Configuration Wizard".
Once done, cycle services again and determine if you can use BE to perform a backup to the drive in question.