Thanks for the ideas guys, I solved the issue by re-installing a clean version of the latest graphics drivers. I googled “nvwgf2umx” and saw that many people were experiencing UE game failures with that reference, and in each case a clean driver installation fixed it. It wasn’t enough to merely install latest drivers, I had to reset all user settings also.
So I guess there is a setting in NVidia settings that can cause UE games, including Unreal Engine editor itself, to fail.