I was having issues with my avatar, the head was attached to a bone that Mecanim did not like. I was able to play animations but I was getting a warning. The model is made in blender. I went into blender and attached the head to a bone that Mecanim was ok with. Upon re-import I added the head in the avatar screen and everything looked good. After exiting the avatar screen the model has been torn apart and reassembled in the most puzzling way possible. Now the head is attached where a leg should be, one of the feet is attached where the other leg should be and the other foot is sticking out of his back! The legs are sticking out of the floor not attached to any thing. I sure hope I am not the first one to see this. I will attach a photo.