Created account can't be used to log in

Hi everyone, I'm stucked again.  I've a website and a window form application which used to access the same database.  In order to use some specific functions, users needed to register first.  On website, I just use CreateNewUser wizard and it works fine.  On Window forms, I create a form to enable new user account creation.  On window form, I use the following code to create the user account.
Membership.CreateUser(userNameTextbox.Text, passwordTextbox.Text, emailTextbox.Text, securityQuestionTextbox.Text, securityAnswerTextbox.Text, false, out status);
It works fine.  However, when I tried to log in from the website using the account created in window form, then the problem occur. I can't log in.  It says "Your login attempt was not successful. Please try again." I checked the aspnet_Users and aspnet_Membership table in the database and the created user is there but it's ...