The 75 and ZT Owners Club Forums - "Display driver failed to start" help anyone?

OK,

So I have an Acer Predator desktop PC.

PREDATOR G3-605 - PC - INTEL CORE i5-4590, 16GB, 1TB + 60GB SSD, NVIDIA GTX960 2GB DEDICATED GRAPHICS DVDRW WIN 8.1(500w PSU)

Upgrades:
60GB SSD replaced with 256GB Crucial MX300
16 GB Ram upgraded to 32 GB, again from Crucial
Free Win10 upgrade when new, now at: win10 - 1909...
Latest graphics driver from Nvidia

I use my predator g3-605 for CAD/CAE not gaming.
I have recently started to get an occasional error message for my graphics.(?)
The error message is:
Display driver failed to start, using Microsoft basic display driver instead.

I have contacted both Nvidia and Acer with the same results
"reset to factory defaults"

That will take me back to the original 8.1, which was a pig to upgrade as Microsoft did not recognise the install!! resulting in many phone calls to their support. So I don't really want to do that, also I will have to re-install EVERYTHING, and there is no guarantee that that will solve the problem.

The problem only happens when I run 1 specific program.
Using GPU-Z I noticed on one occasion that the GPU voltage had dropped to zero (VDDC [V] 0.000). At the same time the Ram was 100% utilised.

I have done a RAM test, which came back clear.

Anyone have any suggestions please?
SteveN