I'm dealing with a site built on a RHEL5 server, MySQL 5.0.22 (yeah, I know it's old, tell Red Hat) php 5.1.6-23, Drupal 6.4

I built a VM, dumped the database from the original server, rsynced the entire /var/www/html/ from the old server to the new server, restored the database... and it worked just fine.

Now, I need to replicate this site again, but on two VMs... one for the web server, one for the database server. I thought it would be pretty straightforward to add a MySQL user on the db host that's allowed to connect from the IP of the web host, but it just... will... not... work! I can, from the shell of the web server, connect to MySQL on the remote server just fine. Both Drupal and phpMyAdmin just will not connect... phpMyAdmin says "#2003 - The server is not responding" and Drupal tells me the site is off-line. When I try to access the install.php, it says:

Failed to connect to your MySQL database server. MySQL reports the following message: Can't connect to MySQL server on '172.16.1.1' (13).

Please keep in mind, though, that I absolutely can connect with the 'mysql' command at the shell. It seems like there's some magic sauce that PHP is missing. I do have php-mysql installed on the web server.