Yahoo mail question ?

On my Yahoo email account, when I sign in and type the first letter of my user name, all the users on the computer come up - I used to be able to just click on mine and my password would enter by itself. I recently changed my password, but the sign in doesn't seem to understand this and an old password comes up instead of my new one - how can I clear my old password from my email ? I've tried changing the "keep me signed in for 2 weeks" thing, but I still get the old password.