A US District Court for the Northern District of Illinois has just granted a temporary restraining order to freeze all US assets of Mt. Gox, Tibanne KK and Mt. Gox CEO Mark Karpeles as part of an effort to find out exactly what caused the Japan-based Bitcoin exchange to fall. This follows the news that Mt. Gox filed for bankruptcy protection in both Japan and the US, a month or so after the exchange went dark and claims it lost nearly 850,000 Bitcoins (roughly $541 million) due to "weaknesses in the system." The restraining order was filed by Edelson PC, the firm Gregory Greene hired to press class action charges against Mt. Gox for fraud. As Mt. Gox is based in Japan, it's unclear what assets there are to actually seize in the US, but the restraining order at least lets Greene's lawyers start the formal process of getting documents and information from the Bitcoin exchange. Perhaps we'll then finally uncover the secret behind its downfall; it'll at least be one Bitcoin mystery solved, anyway.