NSTimer getting faster

I am trying to use to timer to keep track of a time in 开发者_运维知识库a game. Here is the code for the timer. How come every time I relaunch the game from the main menu the timer gets almost twice as fast. Is it because i am not invalidating the timer before I quit. I tried to invalidate the timer but it just gives the error exc_bad access

-(void) StartTimer {
   TotalSeconds = 0;
   GameCenterTotalSeconds = 0;
   timeSec = 0;
   timeMin = 0;
   timer = [[NSTimer scheduledTimerWithTimeInterval:.1 target:self selector:@selector(timerTick:) userInfo:nil repeats:YES]retain];
   //[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
}

//Event called every time the NSTimer ticks.
- (void)timerTick:(NSTimer*) timer {        
TotalSeconds++;
    GameCenterTotalSeconds= GameCenterTotalSeconds + .1;
    timeSec = timeSec + .1;
    if (timeSec >= 60)
    {
        timeSec = 00;
        timeMin++;
    }
    //Format the string 00:00
    NSString* timeNow = [NSString stringWithFormat:@"Time: %02d:%.1f", timeMin, timeSec];
    //Display on your label
    timeLabel.text = timeNow;
}

//Call this to stop the timer event(could use as a 'Pause' or 'Reset')
- (void) StopTimer {
    [timer invalidate];

    //Since we reset here, and timerTick won't update your label again, we need to refresh it again.
    //Format the string in 00:00
    NSString* timeNow = [NSString stringWithFormat:@"%02d:%02d", timeMin, timeSec];
    //Display on your label
    timeLabel.text = timeNow;
}

If you don't invalidate the timer before you exit, the next time you start you are creating a second timer, so events are firing twice as often.

just invalidate the timer, and create a new faster one