I'm getting the ubiquitous 'Error establishing database connection' error on a WordPress install that previously was working okay. I've verified that I can connect from the web server host to the database host via the straight MySQL command line client, using the same MySQL username, database name, hostname, and password as are specified in wp-config.php. It appears to just be an issue with making the connection via WordPress's PHP script.
Running phpinfo on the web server reveals that PHP was compiled with MySQL support, using the following client library: Client API version mysqlnd 5.0.10 - 20111026 - $Id: b0b3b15c693b7f6aeb3aa66b646fee339f175e39 $.
The server is running MySQL 5.0.22.