s@android:~$ dropbox start
Starting Dropbox...
The Dropbox daemon is not installed!
Run "dropbox start -i" to install the daemon
s@android:~$ dropbox start -i
Starting Dropbox.../usr/bin/dropbox:508: GtkWarning: Theme directory scalable/stock of theme NoirCrystal has no size field
dialog.show()
Attempt to unlock mutex that was not locked
Aborted
s@android:~$
This is most probably no special dropbox bug. Currently there are lots of gtk-applications that don't start giving the message "Attempt to unlock mutex that was not locked", see http://sparkylinux.org/forum/index.php?topic=2638.0