calling FacebookClient.PostAsync from silverlight canvas app generates MethodAccessException

I am calling this from a silverlight app:

// docs at: http://developers.facebook.com/docs/reference/api/post
            var client = new FacebookClient(_token);
            dynamic parameters = new ExpandoObject();
            parameters.message = title;
            parameters.link = linkUrl;
            parameters.picture = imageUrl;
            parameters.name = name;
            parameters.caption = promptTitle;
            parameters.description = description;
            parameters.privacy = new
            {
                value = "ALL_FRIENDS",
            };
            client.PostAsync("me/feed", parameters);

This generates the following error: Attempt by security transparent method 'SimpleJson.Reflection.CacheResolver.CreateDynamicMethod(System.String, System.Type, System.Type[], System.Type)' to access security critical method 'System.Reflection.Emit.DynamicMethod..ctor(System.String, System.Type, System.Type[], System.Type, Boolean)' failed.

-- more: --

{System.MethodAccessException: Attempt by security transparent method 'SimpleJson.Reflection.CacheResolver.CreateDynamicMethod(System.String, System.Type, System.Type[], System.Type)' to access security critical method 'System.Reflection.Emit.DynamicMethod..ctor(System.String, System.Type, System.Type[], System.Type, Boolean)' failed. at SimpleJson.Reflection.CacheResolver.CreateDynamicMethod(String name, Type returnType, Type[] parameterTypes, Type owner) at SimpleJson.Reflection.CacheResolver.CreateGetHandler(PropertyInfo propertyInfo) at SimpleJson.Reflection.CacheResolver.MemberMap..ctor(PropertyInfo propertyInfo) at SimpleJson.PocoJsonSerializerStrategy.BuildMap(Type type, SafeDictionary2 memberMaps) at SimpleJson.DataContractJsonSerializerStrategy.BuildMap(Type type, SafeDictionary2 map) at SimpleJson.Reflection.CacheResolver.LoadMaps(Type type) at SimpleJson.PocoJsonSerializerStrategy.TrySerializeUnknownTypes(Object input, Object& output) at SimpleJson.PocoJsonSerializerStrategy.SerializeNonPrimitiveObject(Object input, Object& output) at SimpleJson.SimpleJson.SerializeValue(IJsonSerializerStrategy jsonSerializerStrategy, Object value, StringBuilder builder) at SimpleJson.SimpleJson.SerializeObject(Object json, IJsonSerializerStrategy jsonSerializerStrategy) at SimpleJson.SimpleJson.SerializeObject(Object json) at Facebook.JsonSerializer.SimpleJsonSerializer.SerializeObject(Object obj) at Facebook.FacebookUtils.ToJsonQueryString(IDictionary2 dictionary) at Facebook.FacebookClient.BuildRequestData(Uri uri, IDictionary2 parameters, HttpMethod httpMethod, Uri& requestUrl, String& contentType) at Facebook.FacebookClient.BuildRequestData(String path, IDictionary2 parame开发者_开发知识库ters, HttpMethod method, Uri& requestUrl, String& contentType) at Facebook.FacebookClient.ApiAsync(String path, IDictionary2 parameters, HttpMethod httpMethod, Object userToken) at Facebook.FacebookClient.PostAsync(String path, IDictionary2 parameters, Object userToken) at Facebook.FacebookClient.PostAsync(String path, IDictionary2 parameters) at CallSite.Target(Closure , CallSite , FacebookClient , String , Object ) at System.Dynamic.UpdateDelegates.UpdateAndExecuteVoid3[T0,T1,T2](CallSite site, T0 arg0, T1 arg1, T2 arg2)

was a bug with the sdk at that time. has been fixed since.