Try disabling Xinerama in your configuration file. I had a similar problem and it turned out that Xinerama was causing the RANDR extension to be missing even though the Xorg logs reported that the extension was loaded.
I still have to figure out a way to have both Xinerama and RANDR working.
I also added the following section to my xorg.conf file, but I doubt that it's needed:
Try disabling Xinerama in your configuration file. I had a similar problem and it turned out that Xinerama was causing the RANDR extension to be missing even though the Xorg logs reported that the extension was loaded.
I still have to figure out a way to have both Xinerama and RANDR working.
I also added the following section to my xorg.conf file, but I doubt that it's needed:
Section "Extensions"
Option "Composite" "Enable"
Option "RANDR" "Enable"
EndSection