Why session is being automatically cancelled on FBJS?

Question

here is the code

    FB.ensureInit(function () { 
    var session = FB.Facebook.apiClient.get_session();

    FB.Connect.requireSession(
            function(){
                console.log('connected');
                var fbml = getIviteForm();

                var dialog = new FB.UI. FBMLPopupDialog("Weblings Invite", fbml) ;
                console.log(fbml );
                dialog.setFBMLContent(fbml);
                dialog.show();

            },
            function(){
                console.log('canceled');
            }
    );
});

on the firebug console I can see that it is being evaluated first I can retrive the friends id(in getInviteForm()), bu then I see the "canceled" log, I don't have any idea

PS. I am loged in and no request for logging in is shown