I just performed an upgrade of my Kubuntu installation from 12.10 to 13.04 and had problems with the starting KDE seesion: it wasn’t able to bring up dbus, asked if I were able to call qdbus and quit afterwards.
A short test on the command line calling qdbus brought up a strange error: the binary was there and could be called, but looked for another binary called qdbus in
/usr/lib/x86_64-linux-gnu/qt4/bin/qdbus which wasn’t there. However, there was a binary called
/usr/lib/i386-linux-gnu/qt4/bin/qdbus, and thus I realized that the i386 version of qdbus was installed, rather than the x86_64 version I needed. Thus the fix was easy:
apt-get install qdbus
The i386 version was automatically removed, the x86_64 bit version was installed, and KDE was able to start up properly.