I confirm that this is fixed in Ubuntu-2.6.38-6.34.
Note that natty's patch applied by Andy W can now be dropped:
df74c3984b8888140944fc981d952e08fdc7e7ba Revert "drm/i915: fix corruptions on i8xx due to relaxed fencing"
... has identical content to the patch now in mainline 2.6.38-rc8:
0ee537abbd10a9abf11e1c22ee32a68e8c12ed4a Revert "drm/i915: fix corruptions on i8xx due to relaxed fencing"
I confirm that this is fixed in Ubuntu-2.6.38-6.34.
Note that natty's patch applied by Andy W can now be dropped: 40944fc981d952e 08fdc7e7ba Revert "drm/i915: fix corruptions on i8xx due to relaxed fencing"
df74c3984b88881
... has identical content to the patch now in mainline 2.6.38-rc8: bf11e1c22ee32a6 8e8c12ed4a Revert "drm/i915: fix corruptions on i8xx due to relaxed fencing"
0ee537abbd10a9a