In Xorg.0.log I see: (EE) RADEONHD(0): [dri] CP_INIT failed (EE) RADEONHD(0): RHDDRIFinishScreenInit: RHDDRIKernelInit Failed. After installing the Debian/testing package "firmware-linux", this was solved on my "linux-image-2.6.31-1-amd64" (from "unstable") I used a 1.3.0 radeonhd Xorg driver, but that does not really matter, I think.