A further update:
Switching off Hardware acceleration makes the program work, but the new NVIDIA driver 496.49 has "changed" the way the system works. Previously with NVIDIA 471.35 it would crash during sharpening or noise reduction when processing .CR3 files. Now with version 496.49 it no longer crashes during the develop phase, but when the Develop key is selected the normal develop dialog appears with the moving bar, but it just stays there and stays there, appearing to be doing it's thing...for several minutes, until I stop it with Ctrl+ Alt + Delete and use the task manager to stop the program.
Reverting to switching off hardware acceleration, makes it work, but it is noticeably slower like that.
ALSO the overlays brush in the develop persona is now behaving very strangely and drawing a straight line across the image, from an edge...it's possible to work around using the overlay erase tool, but this is a new issue since 1.10.3