Comment 17 for bug 307306

As an off the wall suggestion, try killing gnome-settings-daemon, then swithing to console for a while, then back to graphics. Your symptoms, and the relation to Xrandr sound like they could be related to a problem I diagnosed earlier where g-s-d would get into a big loop continually firing Xrandr events at the X server, causing it to keep re-probing its outputs.