I have xserver-xorg-video-radeonhd package version 1.2.5 +git20090429.357f190d-0ubuntu0tormod I compiled radeon.ko and drm.ko from git sources and copied them to /lib/modules/2.6.28-11-generic/kernel/drivers/gpu/drm lsmod | grep radeo shows: radeon 379168 1 drm 203424 2 radeon I load the radeon module explicitly in /etc/modules If I take a window and drag it around the screen it redraws fast, but if then I switch to another user keeping the first session open, dragging a window around the desktop is slow. The second X logs sais: (EE) [drm] Could not set DRM device bus ID. (EE) RADEONHD(0): [dri] DRIScreenInit failed. Disabling DRI. The first session does not have this issue. This is an integrated Radeon HD3200 (780G). The logs are attached. I'm running 64 bit version of everything and I used GCC 4.3.3 to build the modules. uname -a shows Linux phenom 2.6.28-11-generic #42-Ubuntu SMP Fri Apr 17 01:58:03 UTC 2009 x86_64 GNU/Linux Any idea why the second session could not set DRM device bus ID? I attached the xorg.conf.