My 6mo dd had the same problem, so we had to gradually get her used to her crib again. First, I would climb in there with her a nights until she was calm and asleep (still took a long time). Then for the first week I slept on a mattress on the floor. Just having me there was a big relief for her. She would wake up every forty minutes or so, and it got to the point where I could just keep lying down and say, "it's okay". I don't know if anyone else does this, but I also removed the crib bumper pad from the side that faces the doorway so she could see around the room, especially so she could see me from the doorway. This helped tons.