Membership.ValidateUser does not use the supplied user name and password
===

We have a winform 2010 app and are using Microsoft's built-in Membership services, we have the database created and there are users in it, however when I try to login 

`Membership.ValidateUser(UserName, Password)` line gives me this error:

    Login failed for user 'mydomain\myusername'.

I have stepped through the code and can confirm that the correct username & password are being sent and that this user is in the SQL database, however instead of authenticating the user with the details passed in it seems my network credentials are used being used for the validation.

This is the web.config:

         <authentication mode="None" />
            
          <!--System.Data.SqlClient-->
          <membership defaultProvider="MembershipProvider">
            <providers>
              <clear />
              <add
                name="MembershipProvider"
                description="ASP.NET Membership database services."
                type="System.Web.Security.SqlMembershipProvider"
                connectionStringName="LocalSqlServer"
                applicationName="/"
                enablePasswordRetrieval="false"
                enablePasswordReset="true"
                requiresQuestionAndAnswer="false"
                requiresUniqueEmail="true"
                passwordFormat="Hashed"
                maxInvalidPasswordAttempts ="5"
                passwordAttemptWindow ="5"
                minRequiredPasswordLength ="7"
                minRequiredNonalphanumericCharacters ="0"
      				/>
            </providers>
          </membership>

The only thing I am not sure is the `<authentication mode="None" />` part, as I have not used Membership services before I am not sure if "None" is causing the problem, if so what it should be?

Any idea why this is happening?

Thanks