When showing an interstitial ad on the device ( HTC Flyer Tablet ) in portrait the ad will show briefly then disappear. Basically it plays thru the initial animation of the ad flipping onto the screen then disappears. Sometimes the x button appears, sometimes not. It always locks the device. You can tap the x button and it will disappear but the semi transparent layer never disappears and the app hangs.
I only have the tablet running 3.2.1 so I cannot check if it does it on other devices running that flavor of android
steve