I got another response (this one from Matt Ko) from SmithMicro.  This is what he said:

"Thank you. I have downloaded Grappo2000's dress from your first image and that problem appears to be caused by the constrained groups she made in the waist area. Used correctly, constraining should work fine, but there can be cases where using constraining in awkward areas or overusing constraints can cause polygons to be positioned in an unnatural way that makes calculations more difficult, thereby creating unpredictable results."

I've also had this problem, so I need to go through my old renders and find one that plainly illustrates the issue.  They need a scene inventory to evaluate what's going on.  I've read complaints about SmithMicro, but they've never experienced poor service from them.  If the rest of you are having this problem with cloth simulations, I think they should hear from you, too!