The new 4.02b is good. It resolves the problems that were originally being had with the update. So it's not taboo any longer. The material problems you're describing here sound similar to what Bloodsong reported having 30-some materials simply vanish out of his scene. That, too, was with Poser imports. Not enough details to say it's exactly the same problem, but it sounds similar enough to make me very suspicious about it. :/