In Ubuntu nautilus is the default file manager even if you use TDE, KDE or any other desktop environment. From kcontrol: Even if konqueror is at the top of the list, some applications will still open files and directories through nautilus. This is exceptionally annoying so I’m going to present a quick and effective method how to change that once and for all.
sudo cp /usr/share/applications/nautilus-folder-handler.desktop /usr/share/applications/nautilus-folder-handler.desktop-backup
sudo nano /usr/share/applications/nautilus-folder-handler.desktop