Comment 33 for bug 684992

(In reply to comment #16)
> Any suggestions on how we could go about further diagnosing this problem, or
> any branches/patches we should try testing?

Keep trying newer versions of r600g and the kernel. Ideally you could find a small test that can reliably reproduce the problem. You might also try enabling tiling:
Option "ColorTiling" "Enable"
in the device section of your xorg.conf