SOLVED
If you should have this problem the only way I could fix it was to do clean install of Cubase and Halion Sonic:
- Uninstall Cubase,and all associated programs and content that come with it
- Uninstall Halion Sonic
- Go into C:/Users//AppData/Roaming/Steinberg - and delete anything associated with Cubase components in 1 and Halion Sonic (noting this directory contains all your user preferences as well so don’t just randomly delete, either take care or perform a backup - in fact just perform a backup in case you miss something)
- Check for any left over Halion related .vstsound files left over from the Uninstall - I had left over copies of HS files in several locations. Windows Search is your friend
- Reinstall Cubase and Halion Sonic 3
My guess, the problem came about from using a Cubase UPGRADE install rather than a Full installer, combined with Halion Sonic upgrading over the top of the HS2 installation. Given the number of left over files from the uninstall process I had to remove the installer clearly just can’t keep up with historical uipdate process scattered across my machine.