Cannot connect with LoginWindows service

Hello,

I have downloaded the Microsoft Dynamics SL 2015 CU1 hyper-v image from partners site.

Now, I'm writing a program to connect to Dynamics SL via WebServices.

I am able to connect with LoginForm service, and read/write some data.

To be able to create data for another user, I think I have to use LoginWindows service to create a session instead of Loginform service.

Unfortunately, I cannot. I have this error message in WebServiceLogs:

LoginWindows Non SL Exception Invalid attempt to read when no data is present.
   at System.Data.SqlClient.SqlDataReader.CheckDataIsReady(Int32 columnIndex, Boolean allowPartiallyReadColumn, Boolean permitAsync, String methodName)
   at System.Data.SqlClient.SqlDataReader.TryReadColumn(Int32 i, Boolean setTimeout, Boolean allowPartiallyReadColumn)
   at System.Data.SqlClient.SqlDataReader.GetValueInternal(Int32 i)
   at System.Data.SqlClient.SqlDataReader.GetValue(Int32 i)
   at Microsoft.Dynamics.SL.WebServices.Session.LoginWindows.LoginWindows(LoginWindowsContext context)

Is there a way to have more log detail?

Can someone help me with that?

Thank you in advance.