Nstimer se bloque lorsque j'appelle [la minuterie isvalid] ou [la minuterie invalide]

J'ai deux nstimers dans mon application iPhone. DÉCRENASEASETIMER fonctionne bien, mais Timercountseconds se bloque lorsque j'appelle [Timercountseconds Isvalid] ou [Timercountseconds Invalidate]. Ils sont utilisés comme ceci:

-(id)initialize { //Gets called, when the app launches and when a UIButton is pressed
 if ([timerCountSeconds isValid]) {
  [timerCountSeconds invalidate];
 } 
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { //Gets called, when you begin touching the screen
 //....
 if ([decreaseTimer isValid]) {
   [decreaseTimer invalidate];
  }
 timerCountSeconds = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(runTimer) userInfo:nil repeats:YES];
 //....
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {//Gets called, when you stop touching the screen(not if you press the UIButton for -(id)initialize)
 //...
 decreaseTimer = [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(decrease) userInfo:nil repeats:YES];
 //...
}
-(void)comept3 { //Gets calles when you rubbed the screen a bit
    if ([timerCountSeconds isValid]) {
    [timerCountSeconds invalidate];
    }
}