Resetting a myqsl root password
Here how to erase the root password (of course you need administrator privileges on the computer).
sudo /etc/init.d/mysql stop
sudo mysqld_safe --skip-grant-tables &
mysql
In the mysql console:
UPDATE mysql.user SET Password=PASSWORD('MyNewPass') WHERE User='root';
FLUSH PRIVILEGES;
Stop mysql_safe server (with a kill) and
sudo /etc/init.d/mysql start
Now it's time to see in the logs who has changed this *$%#! password.