I have had similar effects from almost all of my bodies, and it always came down to a bad CF card. Every time I get these split-image issues it was always before a CF card crapped out on me. So far it's happened twice, and both times the card was the culprit.
I've also seen this issue come up from other people, and it's been related to reading/writing to the card, and an issue with the software in the body. I haven't had that type of problem yet, but I'm sure it can easily happen.
And yes, I've had CF cards go bad in my 40D. It happens unfortunately, sometimes they go bad. I had an 8 Gig Sandisk that gave me about 15 shots like yours in a matter of an hour or so, and not too long after that the card finally just stopped working. Couldn't retrieve photos (luckily at the time there weren't many on it), couldn't format it either in the camera or on the computer, it was dead. So I switched to another card and the problem was gone.