I registered for OD, but not for PX. So apparently the prc file is in a weird, DRM'd but un-keyed state until you logon, which sends the PID to BoB and then encrypts the book. I guess, it's all speculation. But when I tried to deDRM the original download, I get the results I posted about here. Thinking it through and finding and using the file from the Mobipocket "My eBooks" folder, I get the results I want.