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Try deleting the problematic app and then re-downloading the app from the app store.
You can re-download content purchased from the app store using the purchased option from the Quick Links section in the top right corner of the iTunes homepage in your iTunes application on your computer.
You can re-download content purchased from the app store using the purchased option which is revealed by tapping the updates option at the bottom of the screen of the App store app on your iOS device.
If the problem re-occurs, select the content which is causing a problem and use the 'Report a problem' button in Your Purchase History using your computer.