The NVIDIA X driver does not yet support RandR 1.2. Support is planned for a future release, but no schedule has been set yet for when it will be finished. On xorg-server-1.3.0 and higher, current NVIDIA drivers should support everything provided by RandR 1.1.
As for the crash you're seeing, please see http://nvnews.net/vbulletin/showthread.php?t=58498
[Edit: Hit the post button too soon]