I came with this problem when the system alert appeared to remind me a 11:20 meeting while I was playing a video using MPMoviePlayerViewController within my app. After the joyful sound of the alert, I clicked "CLOSE", and after several seconds, the app crashed leaving me a  "_serverConnectionDiedNotification. Info -- notification=Error Domain=AVFoundationErrorDomain Code=-11819 "Cannot Complete Action"" log. 

The link above helped me out. Movieplayer.useApplicationAudioSession is to "give you control over how the movie player content interacts with your audio and with audio from other apps". I guess the crash is due to conflict between  the alert sound and the movieplayer itself.