Index: wp-admin/admin-ajax.php
===================================================================
--- wp-admin/admin-ajax.php	(revision 18378)
+++ wp-admin/admin-ajax.php	(working copy)
@@ -262,6 +262,8 @@
 			continue;
 		if ( !($cat_id = term_exists($cat_name, $taxonomy->name, $parent)) ) {
 			$new_term = wp_insert_term($cat_name, $taxonomy->name, array('parent' => $parent));
+			if ( is_wp_error( $new_term ) )
+				continue;
 			$cat_id = $new_term['term_id'];
 		}
 		$checked_categories[] = $cat_id;
@@ -495,6 +497,8 @@
 			continue;
 		if ( !$cat_id = term_exists( $cat_name, 'link_category' ) ) {
 			$cat_id = wp_insert_term( $cat_name, 'link_category' );
+			if ( is_wp_error( $cat_id ) )
+				continue;
 		}
 		$cat_id = $cat_id['term_id'];
 		$cat_name = esc_html(stripslashes($cat_name));