Why Why Why

Someone PLLLLLEASE tell me what is wrong with the girl child!! She is 25 months old and has been sleeping through the night since she was like a month old or so. Now all the sudden, well actually like a week ago, she's been waking up in the middle of the night yelling for me, asking for her door to be opened. This morning at 4:30am we went round and round over this problem until 6:30am. Yes, I slept late too. I don't understand what her problem is about wanting the door opened. Why all the sudden? I've had several talks with her about it. At first she was wanting to sleep on the couch when she started all this. The girl child is having major issues I think. And I don't get it. Well, through out the day I ask her where she's going to sleep at night and she points to her and says, "In bed!" And I tell her, "Yes, that's right. No more couch." and she says, "Ma'am Ma'am" meaning yes ma'am. Awww, isn't that too cute??!?? I'm just confused about this, because she's never been one to be scared of the dark or need a light in her room. She's ALWAYS been a wonderful great sleeper. HELLLLLP ME!!!! THIS IS NUTS!!!!