Index: wp-admin/includes/ajax-actions.php
===================================================================
--- wp-admin/includes/ajax-actions.php	(revision 23479)
+++ wp-admin/includes/ajax-actions.php	(working copy)
@@ -655,7 +655,7 @@
 	$tags = get_terms( $taxonomy, array( 'number' => 45, 'orderby' => 'count', 'order' => 'DESC' ) );
 
 	if ( empty( $tags ) )
-		wp_die( isset( $tax->no_tagcloud ) ? $tax->no_tagcloud : __('No tags found!') );
+		wp_die( $tax->labels->no_tagcloud );
 
 	if ( is_wp_error( $tags ) )
 		wp_die( $tags->get_error_message() );
Index: wp-includes/taxonomy.php
===================================================================
--- wp-includes/taxonomy.php	(revision 23479)
+++ wp-includes/taxonomy.php	(working copy)
@@ -411,6 +411,7 @@
  * - separate_items_with_commas - This string isn't used on hierarchical taxonomies. Default is "Separate tags with commas", used in the meta box.
  * - add_or_remove_items - This string isn't used on hierarchical taxonomies. Default is "Add or remove tags", used in the meta box when JavaScript is disabled.
  * - choose_from_most_used - This string isn't used on hierarchical taxonomies. Default is "Choose from the most used tags", used in the meta box.
+ * - no_tagcloud - This string isn't used on hierarchical taxonomies. Default is "No tags found!", used in the meta box.
  *
  * Above, the first default value is for non-hierarchical taxonomies (like tags) and the second one is for hierarchical taxonomies (like categories).
  *
@@ -423,6 +424,9 @@
 	if ( isset( $tax->helps ) && empty( $tax->labels['separate_items_with_commas'] ) )
 		$tax->labels['separate_items_with_commas'] = $tax->helps;
 
+	if ( isset( $tax->no_tagcloud ) && empty( $tax->labels['no_tagcloud'] ) )
+		$tax->labels['no_tagcloud'] = $tax->no_tagcloud;
+
 	$nohier_vs_hier_defaults = array(
 		'name' => array( _x( 'Tags', 'taxonomy general name' ), _x( 'Categories', 'taxonomy general name' ) ),
 		'singular_name' => array( _x( 'Tag', 'taxonomy singular name' ), _x( 'Category', 'taxonomy singular name' ) ),
@@ -439,6 +443,7 @@
 		'separate_items_with_commas' => array( __( 'Separate tags with commas' ), null ),
 		'add_or_remove_items' => array( __( 'Add or remove tags' ), null ),
 		'choose_from_most_used' => array( __( 'Choose from the most used tags' ), null ),
+		'no_tagcloud' => array( __( 'No tags found!' ), null ),
 	);
 	$nohier_vs_hier_defaults['menu_name'] = $nohier_vs_hier_defaults['name'];