Huh. That's a good one. Try this: shoot a short set of clips with the 7D at 24, 30, and 60 at various sizes (1080, 480, 720, etc). 5 seconds should be plenty. Open each one in QT and use the inspector to read the files. If you still see issues, make sure you have the most recent updates of Quicktime and your editor.
If software is up to date and the operating system is up to date, the problem may be the camera. Go to Canon's website and verify you have the most recent firmware (the last one was in April), if you do, dump your images and videos off the camera and reset the camera (in the manual p45 - clear all camera settings). I'm pretty sure this will wipe out picture styles and custom settings, but still leave your pix, but I'd rather not take chances since the file structure is FAT16.
If it's still a problem, call Canon.
Hopefully someone more knowledgeable on the more technical nature of the 7D will chime in and tell me it's a simple fix and I'm way off base, but these are the steps I would take.