从Silverlight客户端使用IIS中托管的WF服务时出现问题

我正试图从Silverlight客户端使用IIS express（xamlx）中托管的WF服务。

我添加了我的服务参考，当我使用客户端代理时，我得到的是：

System.ServiceModel.CommunicationException was unhandled by user code
  Message=An error occurred while trying to make a request to URI 'http://localhost:52878/Workflows/PerformanceAppraisal/Exempt.xamlx'. This could be due to attempting to access a service in a cross-domain way without a proper cross-domain policy in place, or a policy that is unsuitable for SOAP services. You may need to contact the owner of the service to publish a cross-domain policy file and to ensure it allows SOAP-related HTTP headers to be sent. This error may also be caused by using internal types in the web service proxy without using the InternalsVisibleToAttribute attribute. Please see the inner exception for more details.
  StackTrace:
       at System.ServiceModel.AsyncResult.End[TAsyncResult](IAsyncResult result)
       at System.ServiceModel.Channels.ServiceChannel.EndCall(String action, Object[] outs, IAsyncResult result)
       at System.ServiceModel.ClientBase`1.ChannelBase`1.EndInvoke(String methodName, Object[] args, IAsyncResult result)
       at CompanyHR.ExemptPAService.ExemptPAClient.ExemptPAClientChannel.EndInitiatePerformanceAppraisal(IAsyncResult result)
       at CompanyHR.ExemptPAService.ExemptPAClient.CompanyHR.ExemptPAService.IExemptPA.EndInitiatePerformanceAppraisal(IAsyncResult result)
       at CompanyHR.ExemptPAService.ExemptPAClient.OnEndInitiatePerformanceAppraisal(IAsyncResult result)
       at System.ServiceModel.ClientBase`1.OnAsyncCallCompleted(IAsyncResult result)
  InnerException: System.Security.SecurityException
       Message=""
       StackTrace:
            at System.Net.Browser.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state)
            at System.Net.Browser.BrowserHttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
            at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelAsyncRequest.CompleteGetResponse(IAsyncResult result)
       InnerException: System.Security.SecurityException
            Message=Security error.
            StackTrace:
                 at System.Net.Browser.BrowserHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)
                 at System.Net.Browser.BrowserHttpWebRequest.<>c__DisplayClass5.<EndGetResponse>b__4(Object sendState)
                 at System.Net.Browser.AsyncHelper.<>c__DisplayClass4.<BeginOnUI>b__1(Object sendState)
            InnerException: 

当我添加我没有使用的服务参考时http://localhost:52878/Workflows/PerformanceAppraisal/Exempt.xamlx

我使用了https版本。但它似乎在使用这个url。

我正在visual studio 2010中使用IIS Express。