Update software
You know that you can update your iPhone/iPod regulary. But while you're doing that, some problems can occur. For example people who updated their iPhone noticed that the home button didn't work anymore and ofcourse they didn't know what the problem was. But it was probably caused by the update, because there was a software problem. A lot of people got this problem when they had IOS 4. But they don't know the causes yet. But don't worry, because now the updates are better and more advanced.