You want to export a Poser figure? I don't see why you want to do this, since you can export a Poser figure from inside Poser in 3ds, obj, etc.
Inside Vue, you can only export Vue objects, items that are in a Vue format, terrains, objects in the vob formats, plants in the veg format, etc...
Now some vob objects cannot be exported, because the maker of the object locked it from export. So it can only be used inside Vue. This is applied to some of the stock objects, and objects you buy at Cornucopia. At Corn, it is clearly stated in the object description if locked or not.