So you try to change your password on T-Mobile's website, and it says:
F451 : Uh-oh, it looks like we have our wires crossed. Please try again later.
So you logout, login again, and try again, and it says the same thing. Then you clear your browser's cache, login again and try again. No dice. What's happening?
Ha! This is T-Mobile's error message for "Your password contains a special character we don't like. Please don't include it." Really. So the special character(s) that appear to elicit the bug are one or more of ":", "%", and/or ")". Don't ask me why. Also don't ask me why T-Mobile's password-change page doesn't tell you about the prohibited character(s), saying only:
Passwords must be 8 - 50 characters, contain one letter and one number, and no common patterns and phrases.
Some mysteries are not meant to be explained.