Shader window's chrome is dark in free version

Are you sure it always happens?

I only had that happen when I had pro running, and switched skin, but if I start Unity with the free skin, it looks just fine

I don't think it's always present, but I've not found an incidental fix for it, by rebooting the software, the plug-in, etc. 

I've only ever used the free version of Unity, if that helps.