In a KDE4 session in current kernel, it is not possible to run any KDE4 program as root. They all exit with the error message:

klauncher(9073) kdemain: No DBUS session-bus found. Check if you have started the DBUS server.
kdeinit4: Communication error with launcher. Exiting!

non-KDE4 programs (including KDE3 ones) run fine as root.