Open up the console and enter "ps -e | grep dbus". There should be two instances. One running as root, and the other as your username. If you have installed updates, you may need to reboot. I had a problem connecting to my sansa-p2 player in amarok. Trying mtp-detect manually, there was an error message dealing with dbus. KDE and Gnome communicate with HAL via the dbus.
While in the console, enter:
polkit-auth --user <username> --show-obtainable
This will show the policies that can be granted. IIRC, you can gain permission with
sudo polkit-auth --user <username> --grant <the policy>
I hadn't noticed a policy editor for kde but have noticed gnome-polkit-editor or something similar.