If the dress is a conforming item, and the spike happens during bending, check that all geometry is inside the fall off zones for that bend using the joint editor. => Enlarge the fall-off zone for that particular bend to cover all geometry.

If the dress is weightmapped? You will have to paint the weightmap for that geometry that "spikes" in that bend.=> Only possible in a Poser-Pro version.

In the latest Poser-Pro versions, you can also simply load the dress obj, go through the fitting room, and let Poser create a fresh cr2 for you.