https://bugs.freedesktop.org/show_bug.cgi?id=42808
--- Comment #3 from Michel Dänzer michel@daenzer.net 2011-11-11 02:56:29 PST --- This may be because the primary device is the integrated Intel GPU, not the Radeon one. Possible solutions might be removing the Section "Device" for the radeon driver (letting it be auto-loaded via the ati driver) or adding a BusID stanza to it.