This happened to me too! I regularly log in between two different locations but I've never encountered a problem. However, I went out of state to visit a friend and when I attempted to login from there I got locked out of my account. I can't log in anywhere but here from my phone because I am still logged in on it and the email in supposed to get to allow me to fix it has definitely not arrived in my email at all... What is the SE security token and how do you get it??