Comment 11 for bug 838181

Okay, that means this commit probably caused your regression.

  commit bbeaf8811ba070fd186dfcabc957044c3a1149ac
  Author: Keng-Yu Lin <email address hidden>
  Date: Wed Jun 22 09:49:34 2011 +0800

      drm/i915: disable PCH ports if needed when disabling a CRTC

For the sake of thoroughness, could you also test the build at:

http://people.canonical.com/~sforshee/lp838181/linux-2.6.38-11.48~lp838181v201109121920/