Hi Deb.Debuggers! :-) The problem has been solved when I upgraded the squeeze xserver packages: xserver-xorg 1:7.3+20 -> 1:7.4+4 xserver-common 2:1.6.3-1 -> 2:1.6.3.901-1 xserver-xorg-core 2:1.6.3-1+b1 -> 2:1.6.3.901-1 xserver-xorg-video-radeon 1:6.9.0-1+lenny4 -> 1:6.12.3-1 xserver-xorg-video-radeonhd 1.2.1-2 -> 1.2.5-1 ... So, as far as I am concerned, this bug can now be closed. Thanks!