Skinned Mesh Snapping to Camera View

Hi, I've got a problem. I've created a model in Blender with an animation, and exported it as an FBX file. However, when I import the skinned model into Unity, the very top of the model snaps to the center of the camera view, leaving a very nasty spike sticking out of my model that follows the camera. How would I fix this? Thanks in advance!

To fix this, I had to go the `Skinned Mesh Renderer` component of my model. Then, I changed the quality of the animation from `Auto` to `1 Bone`. However, I would still like to know why I had to do that. Any ideas? Thanks.

It's a lot simpler if you just save in .blend format, particularly since you can't re-import .fbx into Blender. At any rate it sounds like maybe not all the vertices were properly weighted?