Board Thread:Help Desk/@comment-176.240.53.249-20130207175726/@comment-4674838-20130207182521

There are lots of bugs associated with the Wall of Flesh, as you can read about here:
 * Wall of Flesh

If you've tried dropping the doll into lava multiple times and it keeps happening, you might have to just make a new world and/or new character and try it there.