Bugs / IOS / DragonBox unusable after upgrade to IOS 5
In some cases, upgrading IOS will cause the app to stop working. This isn't a problem with the game.
You might need to restart the device or even to reset it to get your games back.
Read: http://www.ipadforums.net/ipad-os/50464-apps-dont-work-after-ios-5-update.html for more information.