I know why... I couldn't roll back pulseaudio to the needed version without losing half of the apps, so I hacked the libpulse0 files as you saw. Installing something new seems to undo my hack. I'll look into this and see if I can keep that from happening... As for those having "device in use" problems: make sure you run the "close Debian" icon (sudo closechroot from the terminal) before connecting the N900 via USB.