Index: /branches/version-2_11-dev/data/class/pages/admin/order/LC_Page_Admin_Order_Edit.php
===================================================================
--- /branches/version-2_11-dev/data/class/pages/admin/order/LC_Page_Admin_Order_Edit.php	(revision 21222)
+++ /branches/version-2_11-dev/data/class/pages/admin/order/LC_Page_Admin_Order_Edit.php	(revision 21224)
@@ -461,4 +461,7 @@
         // 受注商品の数量を変更
         $arrDest = array();
+        foreach ($objFormParam->getValue('product_class_id') as $n => $order_product_class_id) {
+            $arrDest['quantity'][$n] = 0;
+        }
         foreach ($arrQuantity as $product_class_id => $quantity) {
             foreach ($objFormParam->getValue('product_class_id') as $n => $order_product_class_id) {