I too have been experiencing this same problem and have tried the OpenGL solution to no avail. We even tried to open a previous project with the same codec and that footage now shows up blocky and pixelated. We are using a AJA system in the Mac and had an update last week, other than that we know of nothing else that has changed in our system. Do you by chance use an AJA system as well? We are pursuing that course now but if you do not use AJA then that can be crossed off the list of problems, subsequently putting us back at square one.
Another thing, we also tried sending the FCP sequence through Automatic Duck and that too came out with the same result.
Good luck
Bryan
Bryan Youpa
Editor