Java Security

I have tried using JAAS to authenticate to MS Active Directory and keep getting "javax.security.auth.login.LoginException: Pre-Authentication Information was invalid"

I have tried authenticating with multiple user accounts and on three different realms (Active Directory domains).

How do I need to format the username? I know that when using JNDI to access Active Directory I have to use the format "username@mydomain.com" or the RDN. I have tried it both ways with JAAS kerberos authentication as well as with just the username by itself. I don't think that the username format is the problem though because if I set the account lockout policy to 5 failed attempts, sure enough my account will be locked out after running my code 5 times. Is there something special that I have to do to the password?

I know that there is just something stupid that I'm missing. Here is the simplest example of code that I'm working with:

import java.io.*;

import javax.security.auth.callback.*;
import javax.security.auth.login.*;
import javax.security.auth.Subject;
import com.sun.security.auth.callback.TextCallbackHandler;


public class krb5ADLogin1 {
public static void main(String[] args){

LoginContext lc = null;

try {
lc=new LoginContext("krb5ADLogin1", new TextCallbackHandler());
lc.login();
}
catch(Exception e){
e.printStackTrace();
}
}
}


Here is my config file:

krb5ADLogin1 {
com.sun.security.auth.module.Krb5LoginModule required;
};

The command I use to start the program is:

java -Djava.security.krb5.realm=mydomain.com
-Djava.security.krb5.kdc=DomainController.mydomain.com
-Djava.security.auth.login.config=sample.conf krb5ADLogin1