Earlier today via the official site, as well as through email, players were informed that beginning on April 2nd, 2013, logging in to SWTOR's website or the game client will require you to use your Display Name, rather than your email. This move comes in conjunction with an effort to protect player accounts and information associated with them.
Quote from SWTOR CS
Beginning April 2, 2013, you will only be able to log in to the Game or Website using your
Display Name – Your email address will no longer be accepted from that point forward.
We want to inform you that beginning on April 2, 2013, logging in to the game or website will require your Display Name. Email addresses will no longer be accepted; your Display Name will be the only accepted option.
This new change to the log in procedure is being implemented for several reasons. This change increases the security of our game authentication system, which helps continue to keep the game protected from many security threats including account takeovers.
In case you do not know your Display Name, simply:
Log in to www.StarWarsTheOldRepublic.com
Your Display Name will be shown on the top right-hand side of the website homepage.
You can use your Display Name for logging in to the website and game immediately and we encourage you to do so.
We value our players and we want you to know that the continued security of your account is our top priority.
The Star Wars: The Old Republic Team