The problem is Poser. Poser can't handle a parent child relationship with more than one group. Your thigh groups are trying to weld to both the hip AND the genitals as parents. The fix is to create a small rim of polygons around the genitals that are actually part of the hip group, so that the thighs are only trying to attach to the hip, and the genitals are only trying to attach the hip. I learned about this limitation the hard way after I modeled my Reign of Fire Dragon and couldn't figure out how to bone him. On that version the wing stops at the abdomen, on the original it went mostly all the way down the tail. I wanted a seperate chest, abdomen, and hip group for articulation, and wings that went all the way down the body. Never did figure it out.

mo·nop·o·ly  [muh-nop-uh-lee]
noun, plural mo·nop·o·lies.
1. exclusive control of a commodity or service in a particular market,
or a control that makes possible the manipulation of prices