I just ran a couple of quick tests before heading off to work. Oddly enough if you export a whole figure with subdivision active via Poser's file:export:wavefront obj it produces a viable obj, if you export just a body part it produces an empty obj file. Pretty weird. Importing the poser subdivided mesh into mudbox produces this error but you can see the subdivision levels are recorded in the object list of mudbox. Apparently this information is being recorded somewhere in the obj file. I'll have to do some further digging when I get home tonight...