Remember that account names and passwords are case-sensitive. If you or Support changed your game password, make sure that you're entering the correct case where needed, and that Caps Lock is off. (It's easy to accidentally toggle Caps Lock on--I've done it many times when trying to smack the Tab key, lol.)
Oh, and if you're using an addon that automatically fills the account and password fields, perhaps the account name and password were entered incorrectly.
