I have the iAd test working on my iPhone 5 (ios 6.0), my wife's iPhone 5 (ios 6.1), the 5.1 simulator, the 6.1 simulator, but NOT my 3GS (ios 5.1.1). All I get is the initial loading of the frame for the banner, so I'm only left with a blank/white banner for a couple seconds on load and then it disappears forever.
The 3GS is jailbroken, however, it has never been modified to remove iAds from apps. I even double checked this by opening another app (not mine) that uses iAds and they loaded just fine.
I tried to force-close the app, clean all targets, delete the app and re-loaded, reboot the phone....
Is there anything I may have missed? Any help is greatly appreciated.