Are you using one of the Poser 2 files that contain a dummy neck as the skeleton? I would avoid them for this purpose because they are set up differently. For instance you will find that the dummy neck is not listed in the body parts list and contains no geometry. If you were to edit the CR2 to make it visible you will then find that it would have no control dials. Better to start with one of the Poser 4 figures. Now if I've guessed what you did correctly then the reason for the split is because the chest is connected and welded to the dummy neck, which doesn't exist.

Does that help or just confuse further? :)