First of all, sorry to hear your dog is "scared". My wife and I are big dog people, and I don't know what we'd do without ours. Plus, you always feel bad for them when you don't understand why they are scared, or whatever. They can't talk to you to tell you what's up.
As for the behavior...first off, nice diagram, that really does help to understand....I'd go with Jeff's theory on "something new". Another thing that popped into my head is that possibly one time she came running into the room and slipped/wiped out there and got hurt a little bit. Sometimes dogs can be spooked for awhile after doing something like that. Then again, I'm sure you would have witnessed that, as I doubt your dog is running in there when you guys aren't in there. Anyways, I hope you get it figured out, and she gets more comfortable again.