Veery Weird Problem

Today i opened up my unity editor to proceed on my project. I found this nasty surprise waiting for me:

[18689-unity+2013-11-29+14-17-26-64.jpg|18689]

I reinstalled unity 4 times and tried different versions i even started a new project with no effect at all. Anyone know whats up?

Have you changed the clear flag in your Main Camera?