Index: wp-includes/user.php
===================================================================
--- wp-includes/user.php	(revision 12350)
+++ wp-includes/user.php	(working copy)
@@ -539,7 +539,12 @@
 
 	$query .= " ORDER BY $orderby $order";
 
-	$users = $wpdb->get_results( $query );
+	$cache_id = md5($query);
+	$users = wp_cache_get($cache_id, 'tmp');
+	if ( $users === false ) {
+		$users = $wpdb->get_results( $query );
+		wp_cache_add($cache_id, $users, 'tmp');
+	}
 
 	$output = '';
 	if ( !empty($users) ) {
Index: wp-settings.php
===================================================================
--- wp-settings.php	(revision 12350)
+++ wp-settings.php	(working copy)
@@ -309,7 +309,7 @@
 wp_cache_init();
 if ( function_exists('wp_cache_add_global_groups') ) {
 	wp_cache_add_global_groups(array ('users', 'userlogins', 'usermeta', 'site-transient'));
-	wp_cache_add_non_persistent_groups(array( 'comment', 'counts', 'plugins' ));
+	wp_cache_add_non_persistent_groups(array( 'comment', 'counts', 'plugins', 'tmp' ));
 }
 
 require (ABSPATH . WPINC . '/plugin.php');
Index: wp-admin/includes/user.php
===================================================================
--- wp-admin/includes/user.php	(revision 12350)
+++ wp-admin/includes/user.php	(working copy)
@@ -255,7 +255,14 @@
 	if ( $exclude_zeros )
 		$query .= " AND meta_value != '0'";
 
-	return $wpdb->get_col( $query );
+	$cache_id = md5($query);
+	$user_ids = wp_cache_get($cache_id, 'tmp');
+	if ( $user_ids === false ) {
+		$user_ids = $wpdb->get_col( $query );
+		wp_cache_add($cache_id, $user_ids, 'tmp');
+	}
+
+	return $user_ids;
 }
 
 /**