Marc Adams is not a valid userid.
admin:$1$cce258b2$U9o5nK0z4MhTfB5QlKF23/:admin:admin@mail.org:admin,user
Add the above to your users.auth.php and then login as admin. From there you can go to the user admin panel and create a new user, as required, with a new password.
If you do not have a users.auth.php, then create the following users.auth.php:
# <?php exit()?>
admin:$1$cce258b2$U9o5nK0z4MhTfB5QlKF23/:admin:admin@mail.org:admin,user
Save it to conf.