10 Answers

We have a female who's a bit like that at times, she does it more in the winter when the weather is bad and she can't get outside, she was also like it when our neghbours young kittens started coming in the garden, she bit her tail off 2 years ago when the weather was really bad.

Have you introduced a new cat to you flock, that would make her worse. Or maybe she wants your attention just to herself for a while.

She could be sick. Animals will go off on their own when they are sick. 

Colleen

If it's fleas, there is not "had"...it's still "has". She could be allergic to them if there was scabs. It's extremely hard to get rid of fleas. Even if you kill the adults, their eggs an be dormant for months or years and then hatch out one day and the infestation starts all over again.

Misty, my cat, was so upset when we got a kitten from the humane society, she stayed in my closet for weeks.  They also go off by themselfes if they dont feel well. Try yo give her more attention. If that does not work maybe she needs medical attention.

Is it the same cat you had the recent problem with at night? If so I think she does need to see a vet.

Colleen has a good point.  KItty should be examined by the vet to make sure there's nothing physically wrong with her.  You could try bringing her into the room with you and holding her, petting her.  She may relax after a few days of this.  Possibly something spooked her and she feels safer in the basement.  
 

What about mice,do you know if there are any in the basement ?She might be sitting off waiting for a catch.

  mycatsmom there could be lots of reasons for her doing this

1st as Colleen said she could be ill so a trip down to the vet wouldnt hurt

2nd have you had any work done on the house or moved furniture around upstairs and down stairs as cats HATE change!

3rd its Winter and they do tend to find dark places and she finds it safe down there and maybe warm...if you find she has nothing wrong with her after being to the vet dont let her go down stairs in the basement try and coax her with food and make a bed in where the other cats are and she will feel more comfortable let us know anyway

Here's why. They're upstairs!  http://youtu.be/He82NBjJqf8

Go to an experienced vet. You will be asked a series of questions and based on your answers the vet will know how best to proceed after first a thorough examination of your cat.  Anything else we say would be pure conjecture.  

Thanks, everyone for your good answers. I will take her to the vet. Hadn't thought of that before.