host.walstonet.com is the MySQL server name. This is not always the same as you Webserver, they may be different servers.
This error message is pretty cut and dry. It means the Username and password to connect to the mysql server is being rejected.
dont confuse FTP connectivity with database connectivity, just because your FTP connection is working, it does not mean that there is not a connection problem with the MySQL server, they are completely separate.
In many cases, the MySQL server will be configured to reject outside connections.
You should check with your host to see if this is the case, also check with them to get the correct information to enter for the database connection.