Thanks for the response t-p. However, the following change seemed to have no effect on the list of events.
<?php
$temp = $wp_query;
$wp_query = null;
$wp_query = new WP_Query( array( 'post_type' => 'event', 'meta_key' => 'sortdate', 'order_by' => 'meta_value', 'order' => 'ASC' ) );
$wp_query->query('post_type=event' . '&paged=' . $paged . '');
?>
I’m really stuck on this one.