Comment 8 for bug 65605

Confirmed. Interesting, since this is happening to me on PCI-E X800 card, and you have a card from a totally different series. I have failed a bug about this upstream: https://bugs.freedesktop.org/show_bug.cgi?id=7697

For me changing r300_cmdbuf.c "solves" the problem (ie. does not do checking anymore, which it for some reason fails in doing but works when bypassed), but that file should not even be used in your case, so it might or might not be a bug that is similar.

If you want to dwell into the problem, I'd suggest trying to find where in the kernel radeon drm driver the error happens. See linux-core and shared-core -directories in http://gitweb.freedesktop.org/?p=mesa/drm.git;a=summary , compilable with "make" inside the linux-core directory - then copy drm.ko and radeon.ko to /lib/modules/.../kernel/drivers/char/drm -directory and either reboot or shutdown X (/etc/init.d/gdm stop) and rmmod radeon && rmmod drm && modprobe radeon.