I recently bought a Canon Eos D400, as a way in to digital from film based photography.
I was expecting my lens collection of Canon EF 28-70mm and 70-210mm, Sigma CAF 24mm and 70-210mm lens to work with this camera.
The only one that works is the Canon 28-70mm, which is the least useful to me. the Sigmas display Error 99 messages, and the Canon 70-210mm get a Error 01. I have cleaned the contacts, but they are not dirty anyway.
I think this issue needs to be publicised, as my buying desision was based on the assumption that my older lenses would work.
On the positive side, I like the camera very much and it goes well with my Canon S70, controls being similar and both using compact flash cards.