In my experience packagekit kpackagekit for the gnome and KDE have been broken since 11.1 all you will get are dbus errors. The resolve seems to be dump them and use zypper or YAST which do work without problem.
The weird thing is that it used to work. I can get stuff to install by opening up a termial and using zypper, but double-clicking on an rpm used to work, and now simply doesn’t. Strange. =/