SessionWithConfiguration freezing iOS 8 iPhone 4S on new Xcode 6.0.1

I am having an alarming issue when trying to execute one of my apps on an iPhone 4S with iOS8 and Xcode 6.0.1. What happens is that the control seems to freeze at the last statement of the block:

dispatch_once(&onceToken, ^{
    NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:@"myBackgroundSessionIdentifier"];
    NSLog(@"configuration=%@", configuration);
    configuration.allowsCellularAccess = YES;
    configuration.timeoutIntervalForRequest = 30.0;
    configuration.timeoutIntervalForResource = 60.0;
    configuration.HTTPMaximumConnectionsPerHost = 1;
    session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:[NSOperationQueue
                                                                                                mainQueue]];
});

      

        
        
        
      

    

Note that neither the tested iPad nor the simulator has any problems. Also the same store app compiled with past Xcode seems to have no problem on any device, both according to my testing and lack of user feedback. I was unable to test it on my iPhone 4 as it seems to me that I cannot install the application on it from the new Xcode: it complained that the iPhone is busy when I try to install it.

Someone had a similar problem and knows how to fix it?