I have a possible bug report - if an object is set with visibility turned off on the first frame of a render, it does not appear when visibility is turned back on later in the animation. It was reported on a thread here:
http://www.daz3d.com/forums/discussion/ ... ion#latest
As I reported on that thread, if you do a Reload Scene after the object becomes visibility, it renders OK. I am guessing that invisible objects are screened out to save memory, but then they are not being restored when the visible state changes.