I had a similar problem with drivers 8.24 through 8.27. Roughly one in three logouts, the screen would turn completely white. At that point, Ctrl-Alt-Backspace crashed the computer. After commenting out in xorg.conf: #Option "VideoOverlay" "on" #Option "OpenGLOverlay" "off" it seems to work fine. :-)
-- Lockup problems with both the free xorg ATI driver and the proprietary fglrx driver, using various ATI cards https://launchpad.net/bugs/30447 -- kubuntu-bugs mailing list kubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/kubuntu-bugs