When utilizing an older version of PHP with PHP selector, like 5.2, the issue arises from the MySQL version not utilizing the previous password type (prior to 4.1).

To resolve this error, you can utilize old passwords.
On the server running in mysql

SET PASSWORD FOR ‘some_user’@’some_host’ = OLD_PASSWORD(‘newpwd’);

This will set the password to use the old password version.

Once done, run
mysqladmin reload