Do you still have the problem? Not sure about all that nested stuff, but a problem with the drmRadeonCmdBuffer error should now be fixed (yesterday) in MESA/DRM git repository, http://gitweb.freedesktop.org/?p=mesa/drm.git;a=summary - if you feel like experimenting.
** Changed in: xserver-xgl (Ubuntu) Status: Unconfirmed => Needs Info -- nested Xgl crash, ATI r300 https://launchpad.net/bugs/39759 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs