Also baking is one of those things that so many things can go wrong, and so little silly thing is causing so much trouble and you have to go and launch a major investigation to find out what it is. I know it's a blunt instrument, but have you watched BAKE by Chunck? He goes into all the tips and tricks when it comes to baking. And he's one the best at explaining complex stuff and making it simple. Linking up just in case:
https://cgcookie.com/courses/bake-texture-baking-with-blender
