My nokia n97 died and I don't have a wall charger so I charge my phone on the computer. Anyway I connected it and for a while it wasn't doing anything but now it's gone to a white screen with Nokia on it, and in the top right hand corner there is the little battery symbol which says its charging. How do I turn it back on? I tried turning the on button before but it just turned off and wouldn't turn on again for a while.