Your mysql database username and password is your vista control panel username and password / have you recently changed your vista panel password?
please check your script config file.

You can use a MySQL database with your PHP scripts.  You need to make a database in your control panel under mysql databases:
http://panel.byethost.com/

On that page it will show your DB user, your DB name, and your DB host name.  (and password which is the same as your cpanel password)

Note on free hosting the MySQL server host name is NOT localhost, you need to lookup the host name it does change per free hosting account / server.