https://bugs.freedesktop.org/show_bug.cgi?id=41579
--- Comment #4 from Marek Olšák maraeo@gmail.com 2011-11-07 12:03:14 PST --- Type on master: git log origin/7.11..origin/master -- src/mesa/state_tracker/st_draw.c
(assuming origin is the main mesa repo)
I am 99.9% sure one of those commits fixes it. :) Please try to find the fix by guess. There are only 7 of them.
I don't have r300 or r500 in my machine right now.