If Twiggy's tips don't help, and nothing else seems to work. Then try ASIO4ALL. It always sounds daft to use an asio wrapper on a card which already has asio support - however, some interfaces come with absolutely rubbish asio drivers.
What's the problem with your midi controllers? How does one disrupt the other? Since it is certainly possible to use more than one USB midi controller, you shouldn't be having an issue.