it looks like xmir didn't recover or crashed from a GPU hang

Jul 17 15:50:32 201208-11587 kernel: [  413.356023] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 15:50:32 201208-11587 kernel: [  413.356034] [drm] capturing error event; look for more information in /sys/kernel/debug/dri/0/i915_error_state
Jul 17 15:58:21 201208-11587 kernel: [  881.817296] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 15:58:32 201208-11587 kernel: [  892.805222] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:06:18 201208-11587 kernel: [ 1358.317729] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:07:03 201208-11587 kernel: [ 1403.268344] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:09:01 201208-11587 CRON[2464]: (root) CMD (  [ -x /usr/lib/php5/maxlifetime ] && [ -x /usr/lib/php5/sessionclean ] && [ -d /var/lib/php5 ] && /usr/lib/php5/sessionclean /var/lib/php5 $(/usr/lib/php5/maxlifetime))
Jul 17 16:09:03 201208-11587 kernel: [ 1523.136638] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:11:39 201208-11587 kernel: [ 1678.953429] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:17:01 201208-11587 CRON[2613]: (root) CMD (   cd / && run-parts --report /etc/cron.hourly)
Jul 17 16:19:00 201208-11587 kernel: [ 2119.481397] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:19:53 201208-11587 kernel: [ 2172.399251] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:23:33 201208-11587 kernel: [ 2392.181761] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:25:09 201208-11587 kernel: [ 2488.076395] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:27:03 201208-11587 kernel: [ 2601.927301] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:29:14 201208-11587 kernel: [ 2732.807495] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:31:19 201208-11587 dhclient: DHCPREQUEST of 10.193.37.199 on eth0 to 10.193.37.1 port 67 (xid=0x365bce4b)
Jul 17 16:31:19 201208-11587 dhclient: DHCPACK of 10.193.37.199 from 10.193.37.1
Jul 17 16:31:19 201208-11587 dhclient: bound to 10.193.37.199 -- renewal in 2826 seconds.
Jul 17 16:31:19 201208-11587 kernel: [ 2857.293397] audit_printk_skb: 120 callbacks suppressed
Jul 17 16:31:19 201208-11587 kernel: [ 2857.293424] type=1400 audit(1374093079.342:67): apparmor="DENIED" operation="file_mmap" parent=847 profile="/sbin/dhclient" name="/bin/bash" pid=2724 comm="dhclient-script" requested_mask="m" denied_mask="m" fsuid=0 ouid=0
Jul 17 16:39:01 201208-11587 CRON[2915]: (root) CMD (  [ -x /usr/lib/php5/maxlifetime ] && [ -x /usr/lib/php5/sessionclean ] && [ -d /var/lib/php5 ] && /usr/lib/php5/sessionclean /var/lib/php5 $(/usr/lib/php5/maxlifetime))
Jul 17 16:45:49 201208-11587 kernel: [ 3726.715425] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:49:35 201208-11587 kernel: [ 3952.455386] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:56:11 201208-11587 kernel: [ 4348.032743] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:59:27 201208-11587 kernel: [ 4543.817622] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:59:35 201208-11587 kernel: [ 4551.772900] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
Jul 17 16:59:35 201208-11587 kernel: [ 4551.772959] [drm:intel_pipe_set_base] *ERROR* pin & fence failed
Jul 17 16:59:35 201208-11587 kernel: [ 4551.772966] [drm:intel_crtc_set_config] *ERROR* failed to set mode on [CRTC:3], err = -5
Jul 17 16:59:41 201208-11587 gnome-session[1357]: WARNING: App 'compiz.desktop' respawning too quickly
Jul 17 16:59:41 201208-11587 gnome-session[1357]: CRITICAL: We failed, but the fail whale is dead. Sorry....
Jul 17 16:59:41 201208-11587 gnome-session[1357]: WARNING: App 'compiz.desktop' respawning too quickly
Jul 17 16:59:41 201208-11587 gnome-session[1357]: WARNING: AT-SPI: Could not obtain desktop path or name#012
Jul 17 16:59:46 201208-11587 gnome-session[1357]: Gdk-WARNING: gnome-session: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.#012
Jul 17 16:59:46 201208-11587 colord: device removed: xrandr-XMIR-1
Jul 17 16:59:46 201208-11587 colord: Profile removed: icc-688261ad13288562315b871d09f88a04
Jul 17 16:59:47 201208-11587 acpid: client 1223[0:0] has disconnected
Jul 17 16:59:47 201208-11587 acpid: client connected from 3242[0:0]
Jul 17 16:59:47 201208-11587 acpid: 1 client rule loaded