SimpleAudioEngine stops playing sounds?

Question

For some reason, at first, simpleAudioEngine worked to play all sounds, but then, after a while, they stop working. I am using the simple audio engine to play sound effects that are under 1 second long and are all mp3s, while playing music using AVAudioPlayer. This is the code that I use for the simpleAudioEngine:

//During initialization
[[SimpleAudioEngine sharedEngine] preloadeffect:@"jump.mp3"];
//When effect needs to be played
[[SimpleAudioEngine sharedEngine] playeffect:@"jump.mp3"];