My app, written for the iPad contains several UIButtons. One of them starts and stops an AVAudioPlayer: hitting the button once starts the player, hitting it again stops it accordingly. Rinse and repeat. This all works nicely on iOS version pre 4.2. When installing the App on an iPad with iOS 4.2, the button turns on and off the audio player exactly once, then stops working properly: after hitting the button, it turns into its selected state, but it does not start the audio player (as it should) and hitting the button again doesn't return it to its default state, either. As previously said: it's all fine and dandy pre 4.2, the problem only arises on the most current OS version. XCode 3.2.4 iPad with iOS 4.2