https://bugs.freedesktop.org/show_bug.cgi?id=30313
--- Comment #6 from Gerwin gerwin_kramer@hotmail.com 2010-09-25 05:48:54 PDT --- (In reply to comment #5)
This looks like a tiling issue and r300c doesn't implement tiling fully. I can't reproduce it on R500. Try to set the environment variable RADEON_DEBUG=notiling and please let me know if it fixes the issue.
Yes, RADEON_DEBUG=notiling fixes the issue!