Comment 3 for bug 148437

The following has been known to help with this problem on electricsheep, so might also help here. Add the "VideoOverlay" and "OpenGLOverlay" lines to the Device section for you Radeon card in /etc/X11/xorg.conf:

e.g.:

Section "Device"
        Identifier "Videocard0"
        Driver "radeon"
        Option "VideoOverlay" "on" # add this line
        Option "OpenGLOverlay" "off" # add this line
        VendorName "Videocard vendor"
        BoardName "ATI Radeon X1300"
EndSection

I'd be very interested to know if this fixes the problem, but it probably depends on which ATI graphics card and driver you're using.