How to update Mecanim Transform Mask in inspector when model changes

I'm using a Generic Mecanim rig with a model imported directly from a Blender file (the .blend file is in my Assets folder). If I add a new object to my Blender scene it does not show up in the Transform Mask list in the Animations inspector view. If I import the model into a fresh Unity project the new object appears in the list.

How can I force the inspector view to update? I've tried refreshing, reimporting, restarting Unity, etc. I'm using Unity 4.1.0f4 on a Mac. Any advice would be welcome!