Has anyone found a solution for this problem? I am running into it as well and cannot figure it out! I am using this:
<?php $my_query = new WP_Query(array('tag__not_in'=>array('limitip'),'category_name'=>'features','showposts'=>1));
while ($my_query->have_posts()) : $my_query->the_post();
$do_not_duplicate = $post->ID;?>