See MySQL 5.0 Reference Manual for explaination at:
https://dev.mysql.com/doc/refman/5.0/en/old-client.html
Steps to fix:
1) Open MySQL Command Line Client.
2) Enter your MySQL ‘root’ password.
3) Enter the following command using your wordpress account and password.
mysql> SET PASSWORD FOR
-> wordpress@localhost = OLD_PASSWORD(‘wordpress password’);
