I\'m running WAMP locally, but connecting to a remote MySQL database. The local version of PHP is the latest 5.3.0.
One of the remote databases, being version 5.0.45
Your database server is set to use old passwords by default. The error message you get is mysqlnd seeing a database that can support the new (safer) authentication but refuses to do so. In such a case, mysqlnd aborts the connection and refuses to work.
Make sure your my.cnf does not have
old-passwords = 1
After you comment out that setting from my.cnf (or remove it from where else it might be set), and restart your server, make sure to re-set your password using the command VolkerK describes, otherwise you won't be able to log in.