Could this just be related to bug 771290 <https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=771290>? Because holding off on installing gnome-bluetooth, which would have caused me to trigger that bug, made it so that I didn't encounter this bug, and dpkg appears to work just fine.
To me, it just sounds like that update broke dbus, which in turn broke dpkg, and because of that, dpkg is not what's causing the problem here. Just my two cents, in any case.
