Qt reports wrong Qt::Launch* key

I'm using Qt 4.6.0 on an up-to-date Kubuntu 10.04 system. My computer is a Sony VAIO VGN-SR51MF/S laptop which has several programmable hotkeys. These keys are differently interpreted by Qt and X11; it is as if the mapping is shifted.

Press a key which generates XF86Launch1.
Qt will think Qt::Key_Launch3 is pressed.

Press a key which generates XF86Launch2.
Qt will think Qt::Key_Launch4 is pressed.

Press a key which generates XF86Launch3.
Qt will think Qt::Key_Launch5 is pressed.

Press a key which generates XF86Launch4.
Qt will think Qt::Key_Launch6 is pressed.

Maybe other keys were shifted, too, but I could not check that.

You can see the keys in http://www.youtube.com/watch?v=2Udh_rfhfIo. The keysyms which X11 thinks they are were checked using xev.