I'm no expert, but I believe popover is iPad only. For modal view controller, it should work on iPhone. What happens when you try to present the modal view? Nothing at all?
If you're developing for iOS 5, try PresentViewController instead. Also, try adding an nslog right above the present modal view line to see if the code is being run.
Maybe the problem is the view he is trying to present modally is the uipopovercontroller? In that case he should try to present whatever is the view controller in the popover controller instead.
Why do I keep missing the obvious blind spots (was quite late at my place, mijn excuses).
I should read the topics more thorough.
What I can suggest, when a ModalViewController is not being called in iPhone, but does in iPad, is the pointer you are calling it on, will be probably be void.
that means, you should try calling it on another pointer.