I had this issue right after flashing my 5dmk2.
The video in liveview was jerky and I got a really bad jello effect.
Just go into the menu change the recording modes from 30p, to 24p. Then record a video. Stop and change back to 30p and record a video.
This fixed the jerkyness I was experiencing. Turned off the camera, and turned it back on. Then everything was fine.
Hope this solves it. Now everything seems fine.


