CPTPlotSpaceAnnotation与图像无法在设备上工作，在模拟器中工作

I tried to add an image annotation to a barplot. It works fine in iOS simulator, but the image annotation not shown on the device. I am using Xcode 4.2. Tested on two devices, one is iOS 4.3, another one is iOS5.0.1.I tried to add an image annotation to a barplot