I have been a Debian GNU/Linux user since 2007. Since then, I experienced several major OS upgrades (dist-upgrade). But every time I dist-upgrade, some trouble annoyed me. The most recent problem was related to the seting of Xorg server. When starting up X server (from gdm3), the xserver process couldn't find the glx symbols. In the /var/log/Xorg.0.log: (EE) GLX error: Can not get required symbols. This prevented Compiz Fusion window manager from working on the X desktop. Although the hardware video driver was "intel", it seams that some extra glx code for Nvidia caused the trouble. The following command fixed the problem: aptitude purge fglx-glx fglx-driver nvidia-vdpau-driver (I don't know which package was actually problematic.) If you have a glx related problem with the intel graphic controller chip, try removing unrelated packages that supposed be combined with nvidia or Radeon! That save you some (small amount of ) disk spaces :-) B...