Rhino slows then crashes


Recently (maybe since a Windows 10 update?), Rhino starts fine, then the becomes sluggish, menus start to open in slow motion, the menu clicks don’t register and all finally freezes. Happens in both Rhino 5 and 6 Beta with both new and old models - and even with very simple test ones… I have V-Ray installed but it only loads with Rhino 5. Other programs work fine including some huge image-laden Word files and GIMP with some large graphic stuff. Have tried closing all other running programs (as far as I can see from Task manager), but that makes no difference. No sign of virus or malware…

Any thoughts?