cannot be opened with mode "a"

Fatal error: Uncaught exception 'Zend_Log_Exception' with message '"/var/www/phpweb20/data/logs/debug.log" cannot be opened with mode "a"' in D:\AppServ\php6\library\Zend\Log\Writer\Stream.php:66 Stack trace: #0 D:\AppServ\www\php20\htdocs\index.php(12): Zend_Log_Writer_Stream->__construct('/var/www/phpweb...') #1 {main} thrown in D:\AppServ\php6\library\Zend\Log\Writer\Stream.php on line 66 代码如下： 
<?php 
set_include_path (".;c:\php\includes;D:\AppServ\php6\library"); 
require_once('Zend\\Loader.php'); 
Zend_Loader::registerAutoload(); // load the application configuration 
$config = new Zend_Config_Ini('../settings.ini', 'development'); 
Zend_Registry::set('config', $config); 
// create the application logger 
$logger = new Zend_Log(new Zend_Log_Writer_Stream($config->logging->file)); 
Zend_Registry::set('logger', $logger); 
// connect to the database 
$params = array('host' => $config->database->hostname, 
'username' => $config->database->username, 
'password' => $config->database->password, 
'dbname' => $config->database->database); $db = Zend_Db::factory($config->database->type, $params); 
Zend_Registry::set('db', $db); 
// handle the user request 
$controller = Zend_Controller_Front::getInstance(); 
$controller->setControllerDirectory($config->paths->base . 
'/include/Controllers'); // setup the view renderer 
$vr = new Zend_Controller_Action_Helper_ViewRenderer(); 
$vr->setView(new Templater()); 
$vr->setViewSuffix('tpl'); 
Zend_Controller_Action_HelperBroker::addHelper($vr); $controller->dispatch(); 
?> 
哪位大侠能告诉我如何解决～谢谢
问题补充：我改过文件夹的只读属性 再打开又变成了 选中的方块， 
在属性安全中 设置权限 发现里边有很多用户 都设为全部权限也没反应 
我每次都是以管理员身份登录的 还用设置权限么？
请高人指点～