Hit by the HUNG bug again on Raring. However it's reported differently, so could be the different from the originating one on precise and Quantal.

dmesg
[19492.484182] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
[19492.484186] [drm] capturing error event; look for more information in /debug/dri/0/i915_error_state
Xorg.log(EE) 
[mi] EQ overflowing.  Additional events will be discarded until existing events are processed.
(EE) 
(EE) Backtrace:
(EE) 0: /usr/bin/X (xorg_backtrace+0x36) [0x7fcb2d7cb476]
(EE) 1: /usr/bin/X (mieqEnqueue+0x26b) [0x7fcb2d7ac78b]
(EE) 2: /usr/bin/X (0x7fcb2d61b000+0x6d472) [0x7fcb2d688472]
(EE) 3: /usr/lib/xorg/modules/input/evdev_drv.so (0x7fcb27aab000+0x5f44) [0x7fcb27ab0f44]
(EE) 4: /usr/bin/X (0x7fcb2d61b000+0x96927) [0x7fcb2d6b1927]
(EE) 5: /usr/bin/X (0x7fcb2d61b000+0xc0328) [0x7fcb2d6db328]
(EE) 6: /lib/x86_64-linux-gnu/libpthread.so.0 (0x7fcb2c71e000+0xfbd0) [0x7fcb2c72dbd0]
(EE) 7: /lib/x86_64-linux-gnu/libc.so.6 (ioctl+0x7) [0x7fcb2b43b747]
(EE) 8: /usr/lib/x86_64-linux-gnu/libdrm.so.2 (drmIoctl+0x28) [0x7fcb2c516338]
(EE) 9: /usr/lib/xorg/modules/drivers/intel_drv.so (0x7fcb29ebd000+0x39010) [0x7fcb29ef6010]
(EE) 10: /usr/lib/xorg/modules/drivers/intel_drv.so (0x7fcb29ebd000+0x3a1f7) [0x7fcb29ef71f7]
(EE) 11: /usr/lib/xorg/modules/drivers/intel_drv.so (0x7fcb29ebd000+0x60d51) [0x7fcb29f1dd51]
(EE) 12: /usr/bin/X (BlockHandler+0x44) [0x7fcb2d677b94]
(EE) 13: /usr/bin/X (WaitForSomething+0x114) [0x7fcb2d7c87f4]
(EE) 14: /usr/bin/X (0x7fcb2d61b000+0x58811) [0x7fcb2d673811]
(EE) 15: /usr/bin/X (0x7fcb2d61b000+0x4757a) [0x7fcb2d66257a]
(EE) 16: /lib/x86_64-linux-gnu/libc.so.6 (__libc_start_main+0xf5) [0x7fcb2b36bea5]
(EE) 17: /usr/bin/X (0x7fcb2d61b000+0x478c1) [0x7fcb2d6628c1]
(EE) 
(EE) [mi] These backtraces from mieqEnqueue may point to a culprit higher up the stack.
(EE) [mi] mieq is *NOT* the cause.  It is a victim.
(EE) [mi] EQ overflow continuing.  100 events have been dropped.

repeated 3 times every 100 events dropped till 300

(EE) 
(EE) [mi] EQ overflow continuing.  300 events have been dropped.
(EE) 
(EE) Backtrace:
(EE) 0: /usr/bin/X (xorg_backtrace+0x36) [0x7fcb2d7cb476]
(EE) 1: /usr/bin/X (0x7fcb2d61b000+0x6d472) [0x7fcb2d688472]
(EE) 2: /usr/lib/xorg/modules/input/evdev_drv.so (0x7fcb27aab000+0x5f44) [0x7fcb27ab0f44]
(EE) 3: /usr/bin/X (0x7fcb2d61b000+0x96927) [0x7fcb2d6b1927]
(EE) 4: /usr/bin/X (0x7fcb2d61b000+0xc0328) [0x7fcb2d6db328]
(EE) 5: /lib/x86_64-linux-gnu/libpthread.so.0 (0x7fcb2c71e000+0xfbd0) [0x7fcb2c72dbd0]
(EE) 6: /lib/x86_64-linux-gnu/libc.so.6 (ioctl+0x7) [0x7fcb2b43b747]
(EE) 7: /usr/lib/x86_64-linux-gnu/libdrm.so.2 (drmIoctl+0x28) [0x7fcb2c516338]
(EE) 8: /usr/lib/xorg/modules/drivers/intel_drv.so (0x7fcb29ebd000+0x39010) [0x7fcb29ef6010]
(EE) 9: /usr/lib/xorg/modules/drivers/intel_drv.so (0x7fcb29ebd000+0x3a1f7) [0x7fcb29ef71f7]
(EE) 10: /usr/lib/xorg/modules/drivers/intel_drv.so (0x7fcb29ebd000+0x60d51) [0x7fcb29f1dd51]
(EE) 11: /usr/bin/X (BlockHandler+0x44) [0x7fcb2d677b94]
(EE) 12: /usr/bin/X (WaitForSomething+0x114) [0x7fcb2d7c87f4]
(EE) 13: /usr/bin/X (0x7fcb2d61b000+0x58811) [0x7fcb2d673811]
(EE) 14: /usr/bin/X (0x7fcb2d61b000+0x4757a) [0x7fcb2d66257a]
(EE) 15: /lib/x86_64-linux-gnu/libc.so.6 (__libc_start_main+0xf5) [0x7fcb2b36bea5]
(EE) 16: /usr/bin/X (0x7fcb2d61b000+0x478c1) [0x7fcb2d6628c1]
(EE) 
[ 19491.810] (EE) intel(0): Detected a hung GPU, disabling acceleration.
[ 19491.810] (EE) intel(0): When reporting this, please include i915_error_state from debugfs and the full dmesg.
[ 19491.810] [mi] Increasing EQ size to 512 to prevent dropped events.
[ 19491.810] [mi] EQ processing has resumed after 335 dropped events.
[ 19491.810] [mi] This may be caused my a misbehaving driver monopolizing the server's resources.
[ 19508.772] (II) AIGLX: Suspending AIGLX clients for VT switch
[ 19513.181] (II) Open ACPI successful (/var/run/acpid.socket)
[ 19513.181] (II) AIGLX: Resuming AIGLX clients after VT switch

Linux 3.8.0-22-generic #33-Ubuntu 

i915_error_state is clear from ERROR after S3 suspend/resume or because i mounted debugfs only now. Will add it next time this happend.