where did you model it? I would suggest divideing the mesh at the mouth and making it a grouped piece, that would allow you to to bone the mouth and then remake your open/close morphs. I dont have poser pro pack, so i cant bone it for you , sorry. Have you considered dividing the mesh up at the joints and then using the phi builder and joint editor instead? There are a lot more tutorials on this method, perhaps you will have more luck that way.