Comment 67 for bug 883319

One possible answer to my own question is, that AMD's ATI Catalyst driver disables the Xorg RandR extension and enables it's own RandR extention:

from /var/log/Xorg.0.log:
[...]
[ 68.714] (II) fglrx(0): RandR 1.2 support is enabled!
[ 68.714] (II) fglrx(0): RandR 1.2 rotation support is enabled!
[...]
[ 69.541] (II) fglrx(0): Disabling in-server RandR and enabling in-driver RandR 1.2.
[ 69.975] (--) RandR disabled
[...]
[ 69.975] (II) Initializing built-in extension RANDR
[...]
[ 92.101] (II) fglrx(0): Restoring Recent Mode via PCS is not supported in RANDR 1.2 capable environments

Any idea, how to change this configuration?