@wilt, I just found the following warning in my /logs folder; it's issued when the edit_orders script is initially entered (i.e. no $_POST parameters).
Code:
PHP Warning:  Invalid argument supplied for foreach() in C:\xampp\htdocs\testsite\testadmin\includes\classes\AdminRequestSanitizer.php on line 511
Here's the current code, with line 511 highlighted:
Code:
    private function filterMultiDimensional($parameterName, $parameterDefinition)
    {
        $requestPost = $_POST;
        foreach ($requestPost[$parameterName] as $key => $value) {
            $hacked = $requestPost[$parameterName][$key];
            if (isset($parameterDefinition['params'][$parameterName])) {
                unset($requestPost[$parameterName][$key]);
                unset($_POST);
                $_POST[$parameterName] = $key;
                $type = $parameterDefinition['params'][$parameterName]['sanitizerType'];
                $params = isset($parameterDefinition['params'][$parameterName]['params']) ? $parameterDefinition['params'][$parameterName]['params'] : null;
                $newParameterDefinition = array('sanitizerType' => $type, 'params' => $params);
                $this->runSpecificSanitizer($parameterName, $newParameterDefinition);
                $newKey = $_POST[$parameterName];
                $requestPost[$parameterName][$newKey] = $hacked;
            }
            foreach ($hacked as $pkey => $pvalue) {
                if (isset($parameterDefinition['params'][$pkey])) {
                    unset($requestPost[$parameterName][$newKey][$pkey]);
                    unset($_POST);
                    $_POST[$pkey] = $pvalue;
                    $type = $parameterDefinition['params'][$pkey]['sanitizerType'];
                    $params = isset($parameterDefinition['params'][$pkey]['params']) ? $parameterDefinition['params'][$pkey]['params'] : null;
                    $newParameterDefinition = array('sanitizerType' => $type, 'params' => $params);
                    $this->runSpecificSanitizer($pkey, $newParameterDefinition);
                    $requestPost[$parameterName][$newKey][$pkey] = $_POST[$pkey];
                }
            }

        }
        $_POST = $requestPost;
    }
It looks like you'd want to change that to
Code:
    private function filterMultiDimensional($parameterName, $parameterDefinition)
    {
        $requestPost = $_POST;
        if (isset ($requestPost[$parameterName])) {
            foreach ($requestPost[$parameterName] as $key => $value) {
                $hacked = $requestPost[$parameterName][$key];
                if (isset($parameterDefinition['params'][$parameterName])) {
                    unset($requestPost[$parameterName][$key]);
                    unset($_POST);
                    $_POST[$parameterName] = $key;
                    $type = $parameterDefinition['params'][$parameterName]['sanitizerType'];
                    $params = isset($parameterDefinition['params'][$parameterName]['params']) ? $parameterDefinition['params'][$parameterName]['params'] : null;
                    $newParameterDefinition = array('sanitizerType' => $type, 'params' => $params);
                    $this->runSpecificSanitizer($parameterName, $newParameterDefinition);
                    $newKey = $_POST[$parameterName];
                    $requestPost[$parameterName][$newKey] = $hacked;
                }
                foreach ($hacked as $pkey => $pvalue) {
                    if (isset($parameterDefinition['params'][$pkey])) {
                        unset($requestPost[$parameterName][$newKey][$pkey]);
                        unset($_POST);
                        $_POST[$pkey] = $pvalue;
                        $type = $parameterDefinition['params'][$pkey]['sanitizerType'];
                        $params = isset($parameterDefinition['params'][$pkey]['params']) ? $parameterDefinition['params'][$pkey]['params'] : null;
                        $newParameterDefinition = array('sanitizerType' => $type, 'params' => $params);
                        $this->runSpecificSanitizer($pkey, $newParameterDefinition);
                        $requestPost[$parameterName][$newKey][$pkey] = $_POST[$pkey];
                    }
                }

            }
        }
        $_POST = $requestPost;
    }