window xp 操作cacti流量监控报错

我已将mysql、apache、php、cacti装好，所有的配置也按照安装手册上的要求配置，但通过ie访问cacti时（http://IP/cacti），页面显示：
FATAL: Cannot connect to MySQL server on 'localhost'. Please make sure you have specified a valid MySQL database name in 'include/config.php'

我查看cacti的include/config.php，里面的配置都没有错，如下：
/* make sure these values refect your actual database/host/user/password */
$database_type = "mysql";
$database_default = "cactidb";
$database_hostname = "localhost";
$database_username = "cactiuser";
$database_password = "cactiuser";
$database_port = "3306";