Assuming it isn't hacked or unlocked Apple will fix it for you or replace it. But first try a few things:
1. If you are using a USB hub to connect the iPhone, don't. Connect directly to a USB 2 port on your computer.
2. Check the cable and dock; if you have a spare iPod USB cable connect it directly to the iPhone, not through the dock.
3. Verify that you have the latest version of iTunes
4. Try a forced restore. Reboot your computer, start iTunes, connect the iPhone to the computer. Wait. If you get an error, or nothing happens for several minutes hold the sleep/wake and home buttons for a long time (~20 seconds) until you get a message on the screen that it is restoring.
If all of these fail take it to your Apple store.
(Bewerkt door Ijasper om 11:46, 25-05-2010)