MacBook Pro refuses to boot/recover, hangs at "white screen"
If your MacBook Pro was built around 2013, this is most likely a hardware fault to do with the actual GPU itself. It happened to me so I took it to Apple, they ran some diagnostic application on it and basically gave me a new, updated model. Apparently the problem is well known to them. I have some documents on the subject. I will edit/update this post if/when I manage to find the paperwork.  




http://www.apple.com/support/macbookpro-videoissues/