Editor crashes ( nothing works) when material double clicked

I just went into filters > checked materials, and double clicked to look at one of them in material editor,and editor stopped responding.

I have a solid system,not ‘top’, but I have no problems at all with current complex if not complete, scene.

Windows 10 pro, UE 4.15.1 ,and I meet + all requirements .

ATtached image:

, after restart from crash, now shows a huge mess, where selecting ’ texture’ as shown, is empty and shows this weird colored tiny rectangular area, and no textures where before there were many.

Any ideas ?