Here's a rule of logic: every time you get a mail from ArenaNet, Blizzard, EA, Bioware, Funcom, or whomever else you are subscribed to in a game, go to their site and login from there. Then check if everything is right.
Never click links unless you're 100% sure you've done it. For example if you change a password and 20 sec later you get a mail, it's possibly legit(though I don't know how ArenaNet does this, Blizzard just informed you so you'd know in case you didn't authorize the change).
---------- Post added 2012-09-01 at 12:59 PM ----------
I can feel your pain