Please exit the app via the multitasking bar.
Proceed as follows:From the Home screen, click the Home button twice.
Tap and hold on the app.
When it starts to jiggle, tap the
to close it.
Double-click the Home button and try opening the app again.
http://support.apple.com/kb/ht5137
Proceed as follows:
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http://support.apple.com/kb/ht5137