On my first practice run I encountered a 'semi' corrupt San Disk CF card.
Which meant that some images could not be read, but others could.
Strange, very strange, but I put it down to a card which was not in its first flush of youth and it did have a ding in the casing.
So I used one of my loved and trusted Hoodman cards which have never let me down, and are lightning fast.
So test run two, downloaded the card.
Or I tried to.
I could not download all the images.
At 220 frames, the exact same image count as the San Disk which I thought had failed me.
A bit of scrabbling about on the net revealed the fault, which was all mine.
When the Canon 5D Mk1 was launched there was no provision for the monster CF cards that I was using in it, which led to all sorts of CF card problems.
I needed to update the firmware from 1.0.3 to 1.1.1 to make it work with them.
So here I am back to square one, a lesson learned.
If you are going to offer up the shutter of a Canon 5D mk1 to the photography gods in a multi week time-lapse with a fat CF card just make sure you have the right firmware.