Quick time cannot parse file

[lozenger]

Hi, I am trying to import mp4 files from new Sanyo vid cam via card reader. Dragged the files from reader into a folder and double clicked, the first half a dozen or so opened fine in QT, the rest wont open - QT says its not a movie file, I tried dragging into iMovie, it says QT wont parse the file. We have done nothing different in recording them, does anyone have any ideas why some will open but the rest wont? They are saved as MP4s as default, I have tried renaming as .mov but with the same result. Hope you can help x