Looks like you better get your account hooked up with an authenticator.
Blizzard forces two-factor authentication for Diablo III real-money auctions | Ars Technica
Also if you don't have one and would like one for free might I suggest:
winauth - Battle.net / World of Warcraft / Diablo III Authenticator for Windows and Windows Mobile - Google Project Hosting
or
Blizzard Authenticator PC version - How to | TechiePortal