Video not playing in iOS4

I have the following code to play a video when a button is pushed in my app

Code:

- (IBAction)play {
	
	NSBundle *bundle = [NSBundle mainBundle];
	NSString *moviePath = [bundle pathForResource:@"mom" ofType:@"mp4"];
	NSURL  *movieURL = [[NSURL fileURLWithPath:moviePath] retain];
	MPMoviePlayerController *theMovie = [[MPMoviePlayerController alloc] initWithContentURL:movieURL];
	theMovie.scalingMode = MPMovieScalingModeAspectFill;
	[theMovie play];
	
}

It played just fine until I upgraded my iPhone to iOS4. Now the audio will play, but not the video. Is there a reason for this?