You followed all the instructions in the
sticky thread? "Unable to connect" is an issue between the client's computer (Your PC and the login you're using) and the server (Nostalrius' server where your login is stored); I doubt uninstalling and reinstalling WoW on your computer will help it any.
Is both your account name and password shorter than 16 characters in length? Long account names or passwords will have trouble logging in. Can you type your account name and password out in a notepad file on your computer to ensure every letter and number on your keyboard is working correctly? The temporary ban for logging in too many times unsuccessfully is about 30 minutes, give or take. Wait for it to expire and try again.
UPDATE: The new
password reset feature is now live. If you're still getting errors during login, try resetting the password using the e-mail address you registered your account with. Make sure it's less than 16 characters in length.