@Win7Mac: ah sorry, I just now noticed the original guestion, didnt meant to hijack this thread.

Original guestion was that N9 has troubles to download updates from some wlan AP's. Its hard to tell whats the problem there without knowing the exact manufacturer, settings, and inet environment. On some combinations download just happens to fail, sometimes its because wifi gives (or doesnt give) wrong dns servers and resolv.conf cannot find the server, etc. One thing to try might be to try download with many different wlan AP's, at your work, friends place, or internet coffee.