The bug D@vIcHoJD reported should be fixed now. Kossuth, please update, reboot (or killall timenowd), and check again, maybe the changes have an effect on your bug too. It happened to me too. Now at least I have something to test against.

(On the other hand there is no code to unlock the device in timenow, and no combination of powerbutton presses unlocks the device. I don't know what could be happening)

And I found a bug in hildon desktop too Go to the lockscreen and press ctrl+backspace to see what happens.