UIPopoverController & UIImagePickerControl: "Popovers cannot be presented from a view which does not have a window"

I am trying to display a UIImagePickerControl in my iPad app. At first, the debugger told me that I needed to put it in a popover when doing it on an iPad. So I wrote the following code:

UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
imagePicker.delegate = self;
imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
popover = [[UIPopoverController alloc] initWithContentViewController:imagePicker];
[popover presentPopoverFromRect:CGRectMake(0.0, 0.0, 400.0, 400.0) 
                         inView:self.view
       permittedArrowDirections:UIPopoverArrowDirectionAny 
                       animated:YES];

However, now I get the following error: Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Popovers cannot be presented from a view which does not have a window.'

Any suggestions on what I should do? I know that self.view should have a window, but apparently... it doesn't?