On my Ipad 4 I got a notice to update the OS to 10.7 (I think it was that) so I went ahead. It downloaded okay then began the install that is rebooted and the screen showed the usual Apple Logo on the black screen and the white line beside that indicating the instalation progress. Well it only went a very small way and stopped sat there for hours with nothing at all happening. I can't turn Ipad off or get it to do anything else I am stuck with the black screen and the white Apple logo. Any ideas thanks as I am at my whits end?