The lens correction function is turned on! A Class 10 card doesn't help! See:-
http://www.dchome.net/viewthread.php?tid=953758
(Traditional Chinese, Google Translated English Here)
http://www.dchome.net/viewthread.php?tid=953758&page=1#pid11229817
(Traditional Chinese)
I still recall that last time (very recently) I tested the Canon 5D MkII had no such a problem! >:-o