CanvasAuthorize C# SDK Infinite Loop

I'm looking to try and get an MVC3 Canvas app working with the Facebook C# SDK, but am struggling to allow permissions - Below is my code, and when I open the app I get the 'Allow / Deny' dialog but when I click allow I get redirected to my app and the same dialog appears again (And again and so on no matter how many times I click allow)?

I guess I am missing something obvious... If I take the user_groups permission out it works fine, I just can't access the persons groups.

[CanvasAuthorize(Permissions = "user_groups")]
public class HomeController : Controller
{     
    public ActionResult Index()
    {
        IFacebookApplication settings = FacebookApplication.Current;
        if (settings != null)
        {
            //CanvasPage = settings.CanvasPage;
            //AppId = settings.AppId;
        }

        FacebookWebContext facebookContext = FacebookWebContext.Current;
        FacebookSignedRequest signedRequest = facebookContext.SignedRequest;

        var client = new FacebookWebClient(facebookContext.AccessToken);

        dynamic me = client.Get("me");
        var friends = client.Get("me/friends");
        var groups = client.Get("me/groups");
        ViewBag.Name = me.name;
        ViewBag.Id = me.id;

        JavaScriptSerializer sr = new JavaScriptSerializer();

        var fbFriends = sr.Deseria开发者_StackOverflow社区lize<FBFriends>(friends.ToString());

        ViewData["friends"] = fbFriends.data;
        return View("Friends");

    }

}

Any help, tips or code samples greatly appreciated.

make sure u have set the appid and appsecret correctly.

download the source code and checkout the "samples" folder, there are a bunch of asp.net mvc samples.