Double tap on the Home key to get to the multitask bar. Tap and hold on one of the icons until they start to jiggle, and the minus sign appears. Tap the minus sign on the offending app to close it. Tap the Home key again to exit, then try launching your app again.
If that does not work try a Restart, and then a Restore if still not working.
Last thing to try is to delete the app and re-download it from the App Store.
Restart: Hold down the power button until the power off slider appears. Slide it off. When the iPad finishes shutting down, hold down the power button again until the Apple logo appears.
Reset: Hold down the power and home buttons until the Apple logo appears. The iPad will reboot. This usually takes a bit longer than a restart.