php和mysql安装整合问题

在我安装的时候出现这个问题：
Discuz! info: Can not connect to MySQL server

Time: 2009-4-24 3:47am
Script: /bbs/index.php

Error: Access denied for user 'username'@'localhost' (using password: NO)
Errno.: 1045

Similar error report has been dispatched to administrator before.

我该怎么解决呢？