As I hope I’ve made apparent in these two links below, the proper way to launch a file browser as root in KDE is kdesu konqueror:
Unfortunately, in the KDE 4 version of Kubuntu 8.04, if you try to launch Konqueror (the file browser) or Kate (the text editor) with root (or administrative) permissions, you won’t be able to.
By the way, I don’t know if there are any adverse side effects, but I believe you can restore the original functionality by symlinking the executables back to the normal path:
sudo ln -s /usr/lib/kde4/bin/kate /usr/bin/kate
sudo ln -s /usr/lib/kde4/bin/konqueror /usr/bin/konqueror