Eurogamers on their 3DS review stated the same, their Japanese game didn't work on their european 3DS.
i want to say f*** you Nintendo, why they have lock the games as the other features (street pass, friend codes...) are not region lock!
But we must first concentrate ourselves on the way to entertain people, for video games to live. Else, it's a world where sales representative will win, which has as effect to kill creativity. I want to say to the creators all around the world:"Courage, Dare!". Shigeru Miyamoto.