I have the same issue. Sometimes when the main camera is initialised it will auto - focus ok for a few seconds, then suddenly it will de-focus and be stuck on close up focus. It won't manually focus and nothing seems to reset it - with the exception of leaving the phone alone in a cool place for a couple of hours. Strangely, the camera may then trun back on and focus fine for a while. However, I might only get 2 or 3 good shots before the focus locks on close up again.
Nokia don't seem to be publishing anything to us about the issue despite the large number of people complaining of it!