Fatal Error

Try downloading WordPress again and delete then replace your copies of everything except the /wp-content/ directory and wp-config.php file with fresh copies from the download.

I reloaded with a fresh download of WordPress 3.0.1 and still the same error message. Also mad sure the wp-config.php file is in the wp-admin directory.
hmmm

Fatal error: Call to undefined function is_multisite() in /home/lowell71/public_html/blog/wp-includes/wp-db.php on line 505

What function is it calling for? Does there need to be anything in the brackets?

Does it work if you move wp-config.php up one directory (the same directory as the wp-login.php file)?

open wp-includes >> load.php file and see if this code exists (lines 571-586).

/**
 * Whether Multisite support is enabled
 *
 * @since 3.0.0
 *
 * @return bool True if multisite is enabled, false otherwise.
 */
function is_multisite() {
	if ( defined( 'MULTISITE' ) )
		return MULTISITE;

	if ( defined( 'VHOST' ) || defined( 'SUNRISE' ) )
		return true;

	return false;
}