Why my Unity can not run normally?

Create a new object and run it in Unity 4.6.8. I want to operate some operations in the Scence, it will stop working ,but this will be show lastest operation-step I did after I have clicked on maximize windown/ restore windown.
eg: I click on play button in sence,but the play button don’t change to blue color at once.After I have clicked on maximize windown/ restore windown botton, it change color.
Another point 1 : I can normally execute projects I created before bad with this application.
Thanks for answerer;
Another point 2 : It’s still bad after I reinstall Unity application.

@YangEGG
(I created a new object in Unity 4.6.8. I wanted to do some testing, but it stops working) <-----this seems clear,----->not so clear (but this will be show lastest operation-step I did when I have operated maximize windown/ restore windown. If I can right execute projects that is before bad of I created with this application)
Do you mean you are seeing the error code after the program crashes? If so please paste it here… so others can help you…