Scene View Problems

Hello,

I'm new to Unity and I'm doing all the Tutorial stuff right now. I have a problem with the scene View:

• After Selecting an Object
• After Maximizing the Scene View (with "space"), and minimizing it
• After Some things I didnt found out yet

The Scene View seems to be freezed. I cant Move the camera, I cant select anything, the "choosing-rectangle" of the mouse is also gone. But: anything else is working fine. There is only one thing that helps:

restarting unity.

I'm using Win 7 professional. And I have reinstalled unity several times. I did not found anythings about this in the answers-section.

Any help is appreciated.

Greetings