// HelloWorld Layer
 @interface
 HelloWorld : CCLayer {
    cpSpace  *space;
    CCSprite *ball;
 }

- (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    for( UITouch *touch in touches ) {
        CGPoint location = [touch locationInView: [touch view]];

        location = [[CCDirector sharedDirector] convertToGL: location];

        // Determine speed of the target
        int minDuration = 2.0;
        int maxDuration = 4.0;
        int rangeDuration = maxDuration - minDuration;
        int actualDuration = (arc4random() % rangeDuration) + minDuration;

        // Create the actions
        id actionMove = [CCMoveTo actionWithDuration:actualDuration
                                            position:ccp(location.x, location.y)];
        id actionMoveDone = [CCCallFuncN actionWithTarget:self
                                                 selector:@selector(spriteMoveFinished:)];
        [ball runAction:[CCSequence actions:actionMove, actionMoveDone, nil]];

        [ball retain];
    }
}

2011-06-29 20:44:04.121 ballgame[3499:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[HelloWorld spriteMoveFinished:]: unrecognized selector sent to instance 0x605a3e0'