Yeah, I've done that for years. Usually it worked - this time, possibly because I was working with a huge file and cut out something by accident, the parenting info was lost, but the really strange part was the way the UV maps were messed up - that shouldn't have happened, since it loaded the properly-mapped OBJs themselves. I was working with 1 parent and 8 or 9 child props in one PP2 - I think I might try saving each as an individual prop, update each with an OBJ reference, then load them from the library, parent them, and then save the set.