In my app when the user presses a button I start a HTTP asynchronous request (using `[NSURLConnection sendAsynchronousRequest...]`) and change the text of `UILabel` in the `completionHandler` block. This change, however, does not take place when the request is concluded and instead happens around 2-3 seconds later. Below is a code snippet that results in this behavior.

```
- (IBAction)requestStuff:(id)sender 
{
    NSURL *url = [NSURL URLWithString:@"http://stackoverflow.com/"];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    NSOperationQueue *queue = [[[NSOperationQueue alloc] init] autorelease];

    [NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:
     ^(NSURLResponse *response, NSData *data, NSError *error) 
     {
         NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;          
         exampleLabel.text = [NSString stringWithFormat:@"%d", httpResponse.statusCode];
     }];    
}

```

A similar behavior happens when I attempt to create an `UIAlertView` inside the `completionHandler`.

```
- (IBAction)requestStuff:(id)sender 
{
    NSURL *url = [NSURL URLWithString:@"http://stackoverflow.com/"];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    NSOperationQueue *queue = [[[NSOperationQueue alloc] init] autorelease];

    [NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:
     ^(NSURLResponse *response, NSData *data, NSError *error) 
     {
         NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response; 

         if ([httpResponse statusCode] == 200) {
             UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"It worked!" 
                                                             message:nil
                                                            delegate:nil 
                                                   cancelButtonTitle:@"OK"
                                                   otherButtonTitles:nil];
             [alert show];
             [alert release];
         }
     }];    
}

```

A small difference, though, is that the screen dims when `[alert show]` is executed. The alert itself only appears 2-3 seconds later like in the previous scenario.

I'm guessing this is related to how the UI is handled by the app's threads, but I'm not sure. Any guidance on why the delay happens will be greatly appreciated.