Error establishing database… redux

I realize that this question has been posed a million times before, but I can’t get past install.php. “Error establishing a database connection!,” etc., etc. I swear by all that is holy that the information I have put into wp-config.php is exactly what is in MySQL.
I am running CentOS Linux — basically the RHEL RPMs. I prepared a new installation of MySQL 4.0.18 from the RPMs. I compiled PHP 5.0 against the MySQL installation. I logged into MySQL as the root user. I typed CREATE DATABASE wordpress. I then typed USE wordpress. I then typed GRANT ALL ON wordpress TO wordpress IDENTIFIED BY "password". I then logged out of MySQL. I then copied wp-config-sample.php to wp-config, and changed the variables to match what I had set up in MySQL:
define('DB_NAME', 'wordpress'); // The name of the database
define('DB_USER', 'wordpress'); // Your MySQL username
define('DB_PASSWORD', 'password'); // ...and password
define('DB_HOST', 'localhost'); // 99% chance you won't need
I then accessed my site/wordpress/wp-admin/install.php
The rest is well known: “Error establishing a database connection!”
The only clue I have is that in my MySQL log, there is no sign that I have been trying to communicate with the database.
Any help would be gratefully received.