Hi all. I have an iPhone 3g 2.2 firmware and my screen hasn't been working today. The phone still vibrates when i recieve a call or a text but the screen doesn't turn on, i tried resetting it by holding down the power and front button but no response. However, here's the twist.. the iPhone screen works when it is plugged into the wall charger. after i remove the wall charger, the phone goes back to being dysfunctional in about 5-10 minutes. anyone know how to fix this ? thanks in advance !