Wow, this was really scary ... Leaving the Zaurus without battery for some days, pushing Fn-D-M, then hitting reset with the battery lock open really did the trick. Thank you, Antikx. My C1000 is back to life again ...
Lesson learned: Stay calm, take your time before writing off your Z -- and don't meddle with operating systems you don't really understand. "A cobbler should stick to his last."