Question

It crashes only one time and then it works normally.

Here is the project:
http://www.mediafire.com/?p0dy7g5ozkl69jt

Answer 1

You got a memory issue trying to access a released NSURL in your GetXML class…
There:

- (void)main {
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
    >> NSData *xml = [NSData dataWithContentsOfURL:url];
...

To diagnose these, make use of NSZombiesEnabled, explained there.

To fix your crash, make sure you retain or copy your url in your GetXML class :

- (id)initWithURL:(NSURL*)newURL delegate:(id <GetXMLDelegate>)newDelegate
{
    self = [super init];
    url = [newURL copy]; // there
    delegate = newDelegate;

    return self;
}

and to avoid a memory leak, make sure your release that URL

- (void)dealloc {
  [url release];
  [super dealloc];
}

Untested code, but should work… You should re-read Apple documentation about memory management… 😉