After installing OpenSSL (1.0.1x) x64 vision. I pressed the Facebook>Edit Setting, and the Unity Editor crashed.
Before I installed OpenSSL. It worked but OpenSSL was not found.
Here is how I set it up.
I was having the same problem, in Unity 4 and Unity 5. I installed a different version of openssl and it seems to work.
I can't be sure that it was only this change, because I reinstalled a lot of stuff. But this one worked for me.