Are you sure you've followed everything that is written in this thread: https://bitcointalk.org/index.php?topic=497545.0 ?
The instruction to sign a message is linked by gunthar already.
Try contacting Theymos badbear and cyrus via email or here in PM in forum.
Recovering accounts takes a long time and even months. What you can get now is someone from DT to tag the account that it is hacked temporarily and they can remove it once the account is back to your possession.