Index: wp-includes/taxonomy.php
===================================================================
--- wp-includes/taxonomy.php	(revision 7276)
+++ wp-includes/taxonomy.php	(working copy)
@@ -1151,7 +1151,7 @@
 		}
 	}
 
-	if ( ! $term_id = is_term($slug) ) {
+	if ( ! $term_id = is_term($slug, $taxonomy) ) {
 		$wpdb->insert( $wpdb->terms, compact( 'name', 'slug', 'term_group' ) );
 		$term_id = (int) $wpdb->insert_id;
 	} else if ( is_taxonomy_hierarchical($taxonomy) && !empty($parent) ) {
@@ -1161,7 +1161,10 @@
 		$wpdb->insert( $wpdb->terms, compact( 'name', 'slug', 'term_group' ) );
 		$term_id = (int) $wpdb->insert_id;
 	}
-
+	
+	if ( is_array($term_id) )
+		$term_id = $term_id['term_id'];
+		
 	if ( empty($slug) ) {
 		$slug = sanitize_title($slug, $term_id);
 		$wpdb->update( $wpdb->terms, compact( 'slug' ), compact( 'term_id' ) );