Facebook JS Sdk - FB.getLoginStatus = undefined

I'm using Facebook's JavaScript SDK and trying to determine if the user is logged in or not, I have the following code:

        window.fbAsyncInit = function() {       
             FB.init({ 
                appId:'139894666087975', cookie:true, status:true, xfbml:true 
             });

            $('.login_fb').click(function(){
                FB.login(function(response) {
                if(response.session)
                {   
                    if (response.perms) {
                        window.location.reload();
                    }
                }
                },{perms:'email,user_birthday,user_hometown,user_location,publish_stream'});
            });

            FB.getLoginStatus(function(response) {
                                       alert(response.authResponse);
              if (response.authResponse) {
                  alert(response.authResponse);
              } else {
                $.blockUI({ 
                    message: $('#fblogin'),
                    css: {
                        top: '9%',
                        left: ($(window).width() - 700) /2 + 'px',
                        width: '700px',
                        cursor: 'hand',
                        border:  '10px solid #ccc', 
                        }
                }); 
            }
            }); 
        };  

The response.AuthResponse for getLoginStatus is 'undefined', but I am actually logged in with permissions set for this app.

Any idea why it would continue to show as undefined? When I try to login again, it just closes the Facebook box (because I'm already logged in) and refreshes the page, again showing 'undefined'.

Thanks for any help!