I only recently delved into rigging with a lot of help from a friend here, but was having a similar issue with my clothes going to bits when I posed the figure.  After you have grouped the figure and made it conforming, saved it to your library etc etc etc. open a new scene and reimport the item from the obj that Poser created and stuck in your figures folder.  Reweld all the groups again and save that obj back to your folder where it was under the same name.  Then again, start a new scene, bring in Miki4, load and conform the item, it should keep it from going to pieces. 

Hope that helps, if not, it is beyond my meager rigging skills.