Why won't my dog go down the hallway?

So, we've had my dog for about a year now, and she will NOT go down our hallway. She did for the first few weeks, and then she just stopped going down. She will reach out onto it with 3 paws but no more, never four. If we carry her out onto it from the room beside it, she will squeeze her legs once we get her into the hallway even if she's still in our arms. Then, when we put her down in there, she imediately scrambles back to the room before it. Is this just nothing, or...? I know I'm being pretty ridiculous but...