Archived custom post type posts

Hey all,

I am trying to display archived posts from across 2 custom post types but I cannot get it to work.

To display the archive by month I use –

/** Custom function to alter the WHERE protion of the wp_get_archives() query */
add_filter('getarchives_where', array($this, 'getarchives_filter'));
function getarchives_filter($where){
	$where = "WHERE post_type='".POST_TYPE_NEWS."' OR post_type='".POST_TYPE_TLA."' AND post_status = 'publish'";
	return $where;
}
$args = array(
	'type' => $type,
	'format' => 'custom',
	'before' => '<li class="link_arrow">',
	'after' => '</li>',
	'limit' => $limit,
	'show_post_count' => true
);
wp_get_archives($args);

This displays the link just fine and creates links in this format –
https://www.mydomain.com/2011/01

But when I click the link the query that is run searchs for the Post Type post, which doesn’t exist on my site. Because of this the query returns true for is_404(), meaning that I am taken to my ‘404.php’ page as opposed to the ‘archive.php’ page.

I’ve tried using the posts_where filter and the pre_get_posts filter, but neither seem to work. Does anybody know what I need to do to make this right?

Thanks.