Hi; With guidance from upstream in #intel-gfx on Freenode, we were able to track down a regression in 2.13.901 which makes it impossible to use GNOME Shell on some Intel hardware. The issue is related to delivery of timer interrupts.
Fedora's Adam Jackson tracked it down and disabled page flipping until the problem is resolved: http://koji.fedoraproject.org/koji/buildinfo?buildID=205059 The patch is in this: http://kojipkgs.fedoraproject.org/packages/xorg-x11-drv-intel/2.13.901/2.fc15/src/xorg-x11-drv-intel-2.13.901-2.fc15.src.rpm Jesse Barnes recommended that Debian use the same patch until upstream can track down and fix the problem properly. I have rebuilt the Debian package with the patch and confirmed it does work around the problem.
