materials no more editable

[Antonio.A]

Hi all!

My environment:
OS: Windows 10 Home
RAM: 8 GB
renderers: YafaRay and PovRay

Problem:

• Before installing Yafaray and/or PovRay, editing existing materials was OK.
  
• After install YafaRay, I tried to render with it with disappointing results, after that I installed PovRay.
  
• Rendering with PovRay produced a little better results with simple models, while complex models with transparent complex parts are always black (I certainly have to tune PovRay rendering).
  
• In a existing model, as soon I select a surface and center-click to edit the material, after 4-6 s the application shut down.
  
• The same behaviour occurs if I create a new scene with a simple cube and select a face to create a new material.
  

What can I do?
Thank you in advance.