If you lost your password and receive a password reset from https://register.funcom.com/lostpassword, this temporary password does not change your game password. It only works for the account webpage, so attempting use this password for the game will not work.
Once you can log in to your account webpage and update your passwords, then your passwords for the site and game should match.
Otherwise, if you change your password from your account webpage (account.ageofconan.com), it should update for both the site and the game. Again, it can take up to 15 minutes for the changes to take effect in the game, so if you immediately attempt to login to the game with your new password after changing it, it may not work.