UIAlertView exception in reachability
===

I'm new to iOS and I have a problem in dismissing an **UIAlertView** programmatically.

I declared the alert in .h file:
    
    @interface ViewController : UIViewController<UIWebViewDelegate>{
        UIWebView *webView;
        UIAlertView *alert;
    }

    @property(nonatomic, retain) IBOutlet UIWebView *webView;
    @property(nonatomic, retain) IBOutlet UIAlertView *alert;

and in the .m file I use this alert to warn the user about internet connectivity:

    @synthesize alert;
    -(void) checkNetworkStatus:(NSNotification *)notice
    {
    // called after network status changes
    NetworkStatus internetStatus = [internetReachable currentReachabilityStatus];
    switch (internetStatus)
    {
        case NotReachable:
        {
            NSLog(@"The internet is down.");
            self.internetActive = NO;
            alert = [[[UIAlertView alloc] initWithTitle:@"Network Unavailable" 
                                                             message:@"Internet connectivity could not be established!" 
                                                            delegate:self 
                                                   cancelButtonTitle:nil 
                                                   otherButtonTitles:nil] autorelease];
            [alert show];
            break;
        }
        default:
        {
            [alert dismissWithClickedButtonIndex:0 animated:NO];

        }
    }
}

 Now, when the internet connection is down the alert appears. However, when the internet connection get established the program throws exception complaining about bad access to the object. Can anybody tell me what am I doing wrong?