This is a weird one.
GNOME works with the Xorg ATI driver for Radeon QD/7200/r100 without radeon.modeset=0 (anaconda still needs this for installing!) but KDE shows a very scrambled screen.
The major organization is ok, but the bottom panel and popups are unrecognizable except for the outlines; contents are a weave of dots and lines. The bottom panel is outlined ok, but the icons and texts are scrambled.
Dropping back to the vesa driver lets thing work ok.
Anyone else seeing something like this?