You might try deleting the "cookie" for DiscussCooking. Cookies save previous information and deleteing them is the only way to include new data, such as sign-in info. Go into your browser "tools, options, privacy, show cookies button and scroll down until you see "Discusscooking.com" cookie, select it by clicking on it and then press the "remove cookie" button. You should then be able to go back and sign-in with your new information and your user name and password, and then select the "remember me" check box. That should be it. It should remember you from now on.
"Food is our common ground, a universal experience." - James Beard