I ran into a problem that others on the internet are reporting... when shooting video with some (perfectly in-spec) CF cards, the camera will freeze and an "Err 2" will appear in the lcd. There are enough people seeing this problem that a sign-up sheet has started to get names.
The camera locks up completely and the video that was recording disappears from the card.
Anyway, I don't see that anyone in this Canon forum has listed the problem. Does Canon acknowledge this problem exists?
The worst part about this issue is that the video recording that you had been shooting disappears. Some have lost valuable wedding video or other footage for clients.
I am seeing the problem with brand new 32GB Lexar 1000x and 600x CF cards. Usually shows up after just a few minutes of shooting, but it can be random.