Thank you for the information. Anyway I was curious to see what my MAC address was supposed to be, so I removed the battery and peeked at the sticker below it. It seems that taking the battery out for a while made the "unknown key" error disappear, at least for the moment.
Oh, and by the way, what I said earlier about all librebooted macbooks having the same MAC address: I was wrong. The address is not hard-coded, and it will be decided based on the wifi and ethernet chips in the machine. I will update the wiki to reflect these new observations.
