The most likely culprit is bag geometry. There are combinations of geometry that break the subdivision in Poser. An example of this is something called collinear facets. Another that can cause issues is non-manifold surfaces. Poser attempts to detect these and avoid attempting to render them but the possibilities of weird geometry are endless.

The work around is to use the older version of Poser (Yes you can have more than one major version installed on your computer) and remove items from the scene until it will load properly. That at least you'll know what prop or figure is causing problems.