I had the very same problem with my Daughter and the only thing that I could do was to take the crib mattress out of the crib and lay it on the floor with a soft blanket next to it incase she rolled off and just let her sleep there. She did great and at 11 months we bought her a toddler bed and she has slept in it ever sense. I think that they get a fear of the bars and being inclosed. I know you may worry about them getting up and playing but if you leave them and the do play eventually they will fall asleep by them selves. I hope this helps you.