The Ubuntu dbus package is not explicitly setting configure options. The latest version of lp:ubuntu/dbus appears to have introduced a new option (?) which is defaulting to "enabled". The option is "--enable-x11-autolaunch":
./configure
grep "^#define DBUS_ENABLE_X11_AUTOLAUNCH" config.h
(The question mark about is due to the fact that the natty dbus package doesn't seem to have a configure.ac script so can't do a direct diff).
The behaviour now is that if you are running in an environment where there is no X11, you get this error when you first attempt to use a binary/lib that requires dbus:
Unable to autolaunch a dbus-daemon without a $DISPLAY for X11'
This behaviour is different to that with natty. Fix would appear to be to set "--disable-x11-autolaunch" explicitly (and maybe audit the other options to check for changes).
As discussed with Colin, it may be better (and safer) to retain this change since it is now the default in dbus and as such is the new expected behaviour.
Users who may be affected by this change in auto-launch behaviour can either:
1) Arrange for dbus to auto-launch on address they specify using the DBUS_*_BUS_ADDRESS variables.
2) Manually start the dbus-daemon themselves (maybe as a background job to avoid bug 812913).