My son and I both bought 20Ds about a month ago after being on a pre-order list for about two months. Both cameras arrived with version 1.0.5 of the firmware installed. Both were bought with 17/85s. I had pre-ordered a 10/22 that arrived about a week later.
After about 3 weeks of use one of the 17/85s started to show aperature 00 errors and lock up the camera. At first this occurred rarely, say once in 50 or 60 shots. I could be cleared by removing the lens with the power on or off, or by removing the battery(ies), by resetting the camera, or by powering the camera down. This problem became more and more persistent and eventually could not be cleared by any means. It occurred when the lens was on either camera and also on the demo cameras at the dealer. That lens was replaced under warranty and neither the other 17/85 nor the replacement has shown this behavior.
After about two weeks of use the 10/22 started to show the same behavior and was replaced under warranty.
Our other Canon lenses continue to work just fine.
Neither of the 20Ds has been replaced.
While I think the 20D is great I am beginning to wonder what is going on with Canon as I am discovering that this kind of problem goes back several years with other film and digital models.