The simplest fix is often the most effective. Quit the app by double-tapping the Home button to open the task bar. Tap and hold on an app icon until they go all wobbly, and then tap the red minus sign in the upper-left corner of the offending app’s icon to force it to quit. Restart the app, and you’re probably good to go.
Tapping the minus is the iOS equivalent of Command-Option-Escape.
If not, perform a hard reset of your device by holding down the Home and Sleep/Wake buttons. Ignore the “Slide to power off” screen and don’t release the buttons until you see the Apple logo, then let go. Your phone will restart (it might take a while), and chances are your problem will be gone.
Trash the app to make sure it’s really gone.
But if the app is still giving you trouble, give it the heave-ho. Tap and hold on your home screen to get the wobbly icons, then tap the X to delete the app. Sync it back onto your phone via iTunes, and your troubles should disappear…but if not, try downloading a new copy. Delete the old version from iTunes and move it to Trash when prompted. Then “purchase” it again in the iTunes Store and sync to reinstall it on your phone. Don’t worry—unlike movies and music, iTunes won’t charge you again to download an app that you already purchased as long as you’re signed in with the same iTunes account that originally bought the app.
