As the heading states, I can get my AdMob Ad to show in the iOS 5.1 and 6.0 simulator just fine, however, when running my application on my iOS 5.1.1 or 6.0 devices, there is just a blank space where the ad should be served. The code in my .m file is as follows:

bannerView_ = [[GADBannerView alloc] initWithFrame:CGRectMake(0.0,
                                                            411.0 -
                                                            GAD_SIZE_320x50.height,
                                                            GAD_SIZE_320x50.width,
                                                            GAD_SIZE_320x50.height)];
bannerView_.adUnitID = @"**myID**";
bannerView_.rootViewController = self;
[self.view addSubview:bannerView_];
[bannerView_ loadRequest:[GADRequest request]];

//GADRequest *r = [[GADRequest alloc] init];
//r.testing = YES;
//[bannerView_ loadRequest:r];

Furthermore, if I initiate testing of ads (see commented-out section), the test ad shows on both the simulator AND my iDevices, which is baffling me! What am I missing? Thanks for your help.