Screen flicker issue in iOS 6.1

I am working on a target iOS 5.0 project. Everything worked fine until I updated my

device version for iOS 6.1. In this new version, I ran into some flashing problem in one

specific screen. What am I doing as follows

dispatch_async(dispatch_get_main_queue(), ^{            

    [APPINSTANCE performSelector:@selector(loadFadingScreenFromController:)      
    withObject:self afterDelay:0.2];//Method in AppDelegate to for db sync
    [APPINSTANCE setSyncFrom: @"ORDERS"];
});

//pushing a view
OrderList *orderListObj = [[OrderList alloc] initWithNibName:@"OrderList" bundle:nil];
[self.navigationController pushViewController:orderListObj animated:YES];
self.navigationController.navigationBarHidden = NO;

After that, I get a very strange flicker on the iPhone screen. Flicker only happens

with iOS 6.1, versions are smaller than it works. Any help is appreciated.