That happens all the time even though it shouldn't. What I do when that happens is that I go to the app store and get them again. It won't charge you twice. If that doesn't work then plug your iPhone into iTunes. It should go away or load. You might have to get it again but it will never charge you twice for the same app.
Usually it means you've too many apps running in the background and you haven't cleared your history, cache, and cookies (look in settings) in awhile. Try doing that and restart. Your problems will be solved.