Try this - Reset the iPad by holding down on the Sleep and Home buttons at the same time for about 10-15 seconds until the Apple Logo appears - ignore the red slider - let go of the buttons. (This is equivalent to rebooting your computer.) No data/files will be erased. http://support.apple.com/kb/ht1430
iOS 7: Help with how to fix a crashing app on iPhone, iPad (Mini), and iPod Touch
Troubleshooting apps purchased from the App Store
Delete the app and redownload.
Downloading Past Purchases from the iTunes Store, App Store and iBooks Store