iPad Application Crash Causes Reboot memory problems?

I have an application on iPad that crashes causing the reboot. This crash happens somewhere after the method showMap:(Mappe *mappa):

- (void)viewDidLoad {
    moc = [[MapFetcher sharedInstance] managedObjectContext];
    [NSThread detachNewThreadSelector:@selector(fetchMap) toTarget:self withObject:nil];

    [super viewDidLoad];
}

- (void)fetchMap {
    NSAutoreleasePool *threadPool = [[NSAutoreleasePool alloc] init];

    Mappe *mappa;

    mappa = [[[MapFetcher sharedInstance] fetchManagedObjectsForEntity:@"Mappe" 
                                                     withPredicate:[NSPredicate predicateWithFormat:@"Citta == %@", map] 
                                                    withDescriptor:@"Citta"] objectAtIndex:0];
    [self performSelectorOnMainThread:@selector(showImage:) withObject:mappa waitUntilDone:YES];

    [threadPool release];

}

- (void)showImage:(Mappe *)mappa {
    imvMappa = [[UIImageView alloc] initWithFrame:CGRectMake( 0.0, 0.0, 1024.0, 704.0 )];
    [imvMappa setImage:[UIImage imageWithData:[mappa Mappa]]];
    [scrollView addSubview:imvMappa];
    [scrollView setContentSize:CGSizeMake( 1024.0, 704.0 )];
    [scrollView setMinimumZoomScale:0.5];
    [scrollView setMaximumZoomScale:4.0];
    [scrollView setZoomScale:1.0];
    [scrollView setContentMode:(UIViewContentModeScaleAspectFit)];
    [scrollView setClipsToBounds:YES];
    [scrollView setDelegate:self];
    [imvMappa release];
    [loadingImage stopAnimating];
    [waitFor setHidden:YES];
    [scrollView setHidden:NO];
}

scrollView is an outlet, Mappe is a managed object and it should works fine because I use it everywhere in the app and it causes no troubles. I'm really stuck, what can be that can causes crash-n-reboot?

EDIT: Memory Analyzing

I've used Instruments - Memory Monitor to see what's going on, and it tells that at the moment of launch, my app开发者_JS百科lication uses 17 MB of memory, while the allocation says: Live Bytes 883 KB, overall 4MB. I'm a bit confused... When I launch the code above I see: 2MB of Live Bytes (4 ViewControllers) Overall 22 MB, while Memory Monitor says 77 MB of real memory. What should I see to have a real report of the situation?

You have one managed object context and you're passing managed object from one thread to another and then using it. This a no no. Instead, each thread should have its own managed object context and ObjectsIDs are passed between threads. Receiving thread then retrieves managed object from its own managed object context.

More info: http://developer.apple.com/library/ios/#documentation/cocoa/conceptual/CoreData/Articles/cdConcurrency.html