Index: uc_order/uc_order.module
===================================================================
--- uc_order/uc_order.module	(revision 33804)
+++ uc_order/uc_order.module	(working copy)
@@ -1456,7 +1456,9 @@
     $function = $module .'_order';
     // $order must be passed by reference.
     if (function_exists($function) && ($value = $function('total', $order, NULL))) {
-      $total += $value;
+      if (is_numeric($value)) {
+        $total += $value;
+      }
     }
   }