Index: wp-admin/includes/ajax-actions.php
===================================================================
--- wp-admin/includes/ajax-actions.php	(revision 23480)
+++ 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( isset( $tax->no_tagcloud ) ? $tax->no_tagcloud : $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 23480)
+++ 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 terms 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).
  *
@@ -439,6 +440,7 @@
 		'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 terms found.' ), null ),
 	);
 	$nohier_vs_hier_defaults['menu_name'] = $nohier_vs_hier_defaults['name'];