Suddenly scared cat

I have two young cats, about 7 months old each, a male and a female. Both have been "fixed" for a couple months.

Suddenly this morning the female cat has become very skiddish and scared for some unknown reason. She has typically been the dominant of the two, very playful with the male, etc. However, today she has seemed more timid and less interested in play (Although she did play with him and me a bit today.)

She seems to have an appetite and eating well. I palpated her body all over to check for sore areas, and she doesn't seem to have any physical symptoms that are blatant.

When I got up this morning she would not enter my bedroom (unusual), and instead let out two loud, moaning meows. I brought her into the room to find a source for the fear, but she just seems scared of the whole upstairs. She will finally sit in the window after a while of sitting by the bedroom door hoping to escape.

Any ideas?

Sometimes a sudden change in behavior is a sign of illness or pain. You may want to have your vet examine the cat and have a physical cause either ruled out or treated.

I would keep a good eye on her making sure she is using the litter box and eating properly. Like Lori said, it can have something to do with her not feeling well.
Second, sometimes even little things can scare them a whole lot. It could have been a loud noise or even the other cat that scared her. If it was something that happened. It just takes some time for them to be reassured and feel better about the place that made them anxious.

Thanks for the advice. She does have an appetite and is eating. She seems to be fine other than this fear about entering my bedroom. She will now sit outside the door if I am in the room, and tiptoe in a few steps at times. Otherwise her mood has seemed about the same.

I am relatively new to the cat world, so I don't know a whole lot about what to expect from them.