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How to "reboot" an iPad.

Sometimes an iPad freezes or “locks up” and will not respond to any touch movements, and on some occasions even turning the iPad off and on again will not “unfreeze” the device.

The solution to this problem is easy: Hold down the two buttons indicated at left until you see the white Apple logo, then release the buttons. Leave it alone until you see the "unlock" screen. I have waited for up to 5-7 minutes to see the unlock screen, but it a trick that has always worked consistently for me.