I was asked about my past work experience, why I want to study Public Policy (my background is Economics, so she wanted me to specifically mention why I decided to continue with Public Policy rather than Econ), and then couple of questions about career goals.
It might be that different interviewers are assigned for different countries, and that the one assigned for you conducts the interview in a different way. I would not take it as a bad sign, because even if the interviewer did not like your response to the case study, he/she still needs to ask the personal questions in order to rate your answers in comparison to other applicants. Hence it is likely that the lady/gentlemen who interviewed you has a different approach. How long did your interview take overall?