Originally posted by pxpaulx OP, you sure are good at finding camera faults judging by your post history!
In the OP's defence, I yesterday had the opportunity to try a K-5 in a local shop. I brought a number of my lenses along. The salesman was kind enough to take me back to a storage room dimly lit with tungsten light. Lenses that focused properly on the bright showroom floor missed AF focus terribly under low tungsten light on this K-5.
Yes, it certainly could be operator error of some kind. I am not an expert photogapher. I have no experience with the K-7, but my K20D will sometimes miss focus
slightly under this type of condition, but this K-5 was not even close.
Just figured I would share that experience.