Getting domain errors while using FHST twitter engine


I am developing an app in which I need to authorize app, so I am using FHST twitter engine(using oAuth), but I am getting domain error while getting followers, followings, post an image. What could be the reason for getting domain errors. If I use social framework which is available from iOS5, I am not getting domain errors. BTW, which one is the best library for authorization (iOS)?