title: ValidateCredentials() returns FALSE on First Call but TRUE on Subsequent Calls
body: <p>I'm using the following code to authenticate users on my web service:</p>
  
  <pre><code>using (PrincipalContext context = new PrincipalContext(ContextType.Domain, domain))
  {
      return context.ValidateCredentials(userName, password);
  }
  </code></pre>
  
  <p>The obstacle I'm running into is that the first call to ValidateCredentials() is returning false but subsequent calls return true.  I placed a breakpoint at this line and in the Intermediate window I see the same results: first call returns false, second returns true, even though nothing was changed (by me) between calls.</p>
  
  <p>The 'domain' is String.Empty but I've also tried it with the actual domain name and get the same results.</p>
  
  <p>I'm not that versed in network administration so any help would be appreciated,</p>