Cannot login into App Store

I use a MacBook with OS X version 10.8.2. I cannot login into App Store by my AppleID and password although I can login into iTunes. When I try to login App Store using a CORRECT Apple ID INCORRECT password, a message was shown "Your Apple ID or password was entered incorrectly.". Again I try to enter the correct my Apple ID and password then click "Sign in" but there are no affect. After 3 times I click "Sign in", the form is hide automatically.

So what is my problem and how can I solve it?

Please give me a help! Thank you so much!