Okay, I could get the device to a defined state again by opening it up and removing the power supply for a few secs. Now I can reflash it again.
But it seems as if the number of bad blocks was increased drastically by the last nprog attempt.
Please have a loot at
http://pastebin.com/kJicpwFx
Flashing with 0.2.1 or head still does not lead to a booting device.