The initial MySQL accounts have not been setup. When MySQL is installed, there are two accounts named "root"; one for localhost and one for a hostname/IP address. By default, these accounts do not have a password set, you need to set one. Then you also need to setup two separate user accounts with the same user/pass that aren't admin accounts. One for localhost, one for a hostname/IP address.
Right now, you are trying to use MySQL with the root accounts that have no password set for them. This is a HUGE security risk.
Look at the MySQL documentation at http://dev.mysql.com
for information on Securing the initial MySQL accounts and setting up new user accounts. Use that account information in config.php.