I have a 32GB iPhone 4 (GSM) which has been dropped and the screen has been shattered. This is not a big deal, I can replace it, but I'm curious as to the fact that the touch screen working erratically now. Some presses do not register (it seems to go in bars, width-wise across the screen) and scrolling is only possible between the 'dead' zones. Is this something which will be fixed by replacing the display and digitiser? Or is this a motherboard issue?