If you are using KDE or Qt programs but not in a full KDE session (specifically, you did not run “startkde”), then as of KDE 4.6.1 you will need to tell Qt how to find KDE’s styles (Oxygen, QtCurve etc.)
You just need to set the environment variable QT_PLUGIN_PATH. E.g. put
into your /etc/profile (or ~/.profile if you do not have root access). qtconfig should then be able to find your kde styles and everything should look nice again!