sounds like what I have encountered before. It could be qt rather KDE related. My fix was to remove the 'bitmap fonts' from the fontconfig list. Don't know if you are seeing the same error though but sounds familiar, basically my problem is all the standard fonts KDE used(especially KDM) got screwed up(not the font itself, just the way it is presented through fontconfig) which makes QT not happy and the calculation of the positon etc all went wrong. So you see the dialog, the splash etc. but there is no text just a long line(like underscore) across.