Please could you help me with my iPhone 4. I plugged it in to sync it with my PC the updates took over 3 hours. When it had completed, I unplugged it, but it would not turn on. All I get is the iTunes logo and a USB cable on the screen, which stays for about 30 seconds, then the phone switches off. I have tried holding down the on/off button, and the home button at the same time to reset it, but it hasn't helped.
Is there anything I can do, or should I take it to an Apple store? I have had the phone for about 11 months.