I add a function to dismiss the `UIAlertView` after several seconds.The whole code is like:

```

- (void)netWorkAlert
{
    UIAlertView *netWork = [[UIAlertView alloc] initWithTitle:@"error" message:@"network has problems" delegate:self cancelButtonTitle:nil otherButtonTitles: nil];
    [netWork show];
    [self performSelector:@selector(dismissAlert:) withObject:netWork afterDelay:2];
}
- (void)dismissAlert:(UIAlertView *)alert
{
    if(alert)
    {
        [alert dismissWithClickedButtonIndex:0 animated:YES];
        [alert release];
    }
}

```

the `netWorkAlert` is invoked when the network is unavailable.

Now the problem I met is when the `netWorkAlert` is invoked at the second time, the app is broken and the Xcode shows error in

```

int main(int argc, char *argv[])
{
    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([ZJAppDelegate class]));
//Thread 1 :EXC_BAD_ACCESS(code=1,address=xc0000004)
    }
}

```

I didn;t use ARC and I don't know why it crashes. Even I comment the `[alert release];`, it still has the same problem at the second time.

Could anyone help me to check it?
thanks!