Both my 5d Mk3's are locking up intermittently. So far I've lost two wedding ceremonies from these cameras. I'm using genuine Sandisk extreme pro 32gb cards. I'm trying now to induce the problem at home to see if I can work out what is going on. So far it seems to me that the camera may be trying to write a file larger than fat32 will allow. Times the cameras have locked up have been around the moment the camera is about to split the file and start a new file to reach the 29 min mark. When the problem happens the footage starts to skip on the display for about 3 seconds then freezes. Only taking the battery out will unfreeze the camera. The footage of the previous 12 mins is lost completely. Does any one know of a forum dealing with this problem I can join? Canon really need to do something about this ASAP. The camera is useless for events until you can trust it will not loose your footage!