Reinstalling Firefox won't fix issues caused by files in the Firefox Profile Folder unless you would remove all personal data, but that way you would lose everything unless you have backup. ---- Do you mean names and passwords in the Password Manager or do you mean websites remembering you after closing and restarting Firefox? There is a difference between remembering the name and password in the Password Manager and a "remember me" check box on a web page to log you in automatically.<br /> The latter usually involves the creation of a special "remember me" cookie that is stored on your computer and that is send to the server.<br /> If that "remember me" cookie is removed or gets corrupted or is not send to the server then the server won't remember you anymore and you need to sign in once again. * http://kb.mozillazine.org/Cookies * http://kb.mozillazine.org/Password_Manager