drm GPU hung, resume no longer working

Hi,

I am running:

  FreeBSD nucleus 10.0-CURRENT FreeBSD 10.0-CURRENT #87 r247546: Fri Mar
  1 13:15:42 EST 2013     root_at_nucleus:/usr/obj/usr/src/sys/NUCLEUS  amd64

Sometime very recently, resume has stopped working.  I can ssh to the
machine when it resumes, and I do see my background image on resume, but
once the screen goes into locked mode (xscreensaver), I cannot get back
to a working state without reboot.


syslog reports:
  Mar  5 09:21:33 nucleus kernel: error: [drm:pid12:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung
  Mar  5 09:21:33 nucleus kernel: info: [drm] capturing error event; look for more information in sysctl hw.dri.0.info.i915_error_state

dmesg says:
  uhub2: 2 ports with 2 removable, self powered
  ugen0.2: <vendor 0x8087> at usbus0
  uhub3: <vendor 0x8087 product 0x0024, class 9/0, rev 2.00/0.00, addr 2> on usbus0
  ugen2.2: <vendor 0x8087> at usbus2
  uhub4: <vendor 0x8087 product 0x0024, class 9/0, rev 2.00/0.00, addr 2> on usbus2
  uhub3: 6 ports with 6 removable, self powered
  uhub4: 6 ports with 6 removable, self powered
  ugen0.3: <Azurewave> at usbus0
  error: [drm:pid12:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung
  info: [drm] capturing error event; look for more information in sysctl hw.dri.0.info.i915_error_state

hw.dri.0.info.i915_error_state output is at:

    http://people.freebsd.org/~gjb/i915.sysctl.txt

Any thoughts on how to debug this further?

Thanks.

Glen