Well, that's interesting malteser60. Is there any way to figure out what clothing is causing the problem? Because maybe I could just remove whatever it is. Do you think something from The Store could be messing it up? That seems really odd to me!
As I understand it, the clothing in question is mistakenly coded to be available for all sims: adults, children, babies, etc., which is exactly the problem. A child is spawned, the game gives it the corrupted clothing, and it looks like a misshapen monster. And if the game randomizes clothing for an adult sim (like pregnancy), and if the sim gets the child version of the adult clothing, the sim becomes invisible, but looks like a strange stretchy misshapen solid black baby when you go to Plan Clothing. And all clothing will be available, male, female, adult, babies, all ages, but you can't change into it.
And, as I further understand it, the files in question have "nkd" somewhere in the file name. And I've heard the clothing line "American Blonde" is also corrupted.