There are scattered reports of iOS devices (iPads, iPhones, iPod touch devices) hanging or freezing during the iOS update process. Before you begin the update, shut down and restart your iPad or other iOS device. (Rebooting is a good step to help prevent problems before updating any computer or mobile device.)
Press and hold the Sleep/Wake button until a red slider appears. Use the slider to turn the iPad off. Wait a few moments while your iPad shuts down. Then hold the Sleep/Wake button until the Apple logo appears. When you see the Apple logo, release the Sleep/Wake button. Now begin the update process.
If your iPad seems to be stuck or frozen after you attempt to update the iOS, try a hard reset.
Press and hold both the Sleep/Wake button and the Home button until the screen goes blank. Release both buttons. Be patient as the Apple logo appears and your iPad comes back to life. This should solve the problem in most cases.