Interview After Medicals and RPRF

Hey guys,
I really need your help.. Well i applied my case back in 2009 from Sweden to CHC London since i am studying here as a student. Last year in dec 2010 I received my Medicals request and RPRF which i submitted in the same month. However now when i was expecting PPR.Upon contacting CHC London through mail I was told that an interview will be required. Now my question is why would they ask for an interview after medicals,PPR and everything!?Is it normal or is it only me?Most of the cases I have gone through now on this website suggests that interview request after medicals are rare?However I am confused since I don't know what might have flagged this interview!I already have ordered My CAIPS. Can u guys suggest what might have caused an interview request at this stage..Has anyone else experienced the same situation of receiving an interview request after medicals.. If Yes kindly let me know about your experiences and what were the primary questions in such interview...

Regards,
Sohail