Comment 18 for bug 753971

Unity relies on Compiz to handle resolution changes and as you may have noticed, Unity resizes itself correctly. As for the scrambled display, there need to be tighter synchronization between the driver, X and Compiz/Unity to ensure smooth and clean transitions between modes.
We a have a similar issue with the NVidia driver after a Resume (preceded by a Suspend). In this particular case, this is known to be a driver bug.