No success after your suggestion Tim.
I have set a empty password for root on the MD mysql and when I run the dpkg-reconfigure --force mythtv-database:
root@moon130:~# dpkg-reconfigure --force mythtv-database
Failed to execute SQL: GRANT ALL PRIVILEGES ON mythconverg.* TO mythtv@localhost IDENTIFIED BY '3zRkyO86'\nAccess denied for user 'root'@'192.168.80.4' to database 'mythconverg' at -e line 8, <> line 1.
I've not this error when I updated the Core, only the MDs.
I will try to rebuild the MD image and see what's append....
Thank's all of you for your suggestions !