Open iTunes// uninstall the app.// Sync your phone with iTunes (this will get the app off your phone). Download the app again from iTunes from your PC. (NOT YOUR PHONE)// sync app back to your phone through iTunes.
My suggestion would be to never download, install or update an app at your phone (if this is what you did). Always do it through iTunes through your PC and than sync to your phone.
I know it is supposed to work the other way but you will see a lot of people have problems when they download or update apps from their phones.