After going through this on the phone, it appears that the machine in question has some kind of file security system which was causing very strange results.
Briefly:
From file explorer, the user could not see any seckey.tff file in the program files VRTurning directory
However, when he ran regrights.exe (available here:
https://www.denfordata.com/downloads/RegRights.zip ) it DID find a file in the directory, but it was the wrong one (it was a QuickTURN 2D license)
If he copied the proper seckey.tff into the folder, regrights would still find the "phantom" file and say it was quickTURN - the new file was proved to be the correct one by copying seckey.tff and regrights into a new, blank directory and running regrights - this then reported the seckey file WAS for VR Turning.
The problem was solved by deleting the visible seckey from the directory, running regrights and browsing to the same folder and deleting the "phantom" seckey file from within the regrights file browser. Copying in the correct seckey file then sorted it and let VRTurning run.
I can only assume that there is a file system installed, which tries to control or hide access to files it dosn't think you should be changing
PS the customer is now experiencing diffculty opening .fnl files from VR Turning....
They can open the file in notepad and copy and paste the text into the editor, but if the use File>Open, only the 1st character from the file is loaded ! Again I can't really explain what could be causing this, other than a file security or network system setting. TBC...