Unity5 shader problem/bug or do I need to change something?

The built in default shader causes the following distorted image in scene & game & production view in a very simple test project:

Is this a bug or do I need to change something? Thank you in advance for any help!

Dear friend, I tested your project and every thing is fine here! I suppose your problem is the graphic card or some of its driver. Did you update the driver?
Remember to close the question as answered and maybe some thanks…

You have this screen probably when you import a model. I do not import anything. I just use cubes. There is no texture defined, just the default material is used. As I said before, everything is default. Very strange.

The next figure is when I switch Cast Shadows OFF: