having done a bit of reading up it seems that the usb cable from the back of the pc to the ipad might not have a powerful enough charge to charge it !!! all I know is that when I connect to the usb (for itunes sync) the ipad has a message saying NOT CHARGING...and when I connect to to cable attached to the mains it does chanrge. I had hoped to be able to use one cable for both jobs (funnily enough I can do this for my ipod touch) The usb cable that I use to sync the ipad and itunes DOES sync AND charge the ipad touch.