Unable to define superuser password for mysql server on localhost

[ProWebS]

Hello,

After the upgrade of our Plesk installation from 9.5x to 11.5.30
Everything works ok (sites,sites with databases, Plesk etc)

but when I go to Home>Tools & Settings> Backup Manager
I see errors on every daily backup I have on schedule:

The backup Plesk_Daily_Full_Backup_1407060112.tar has completed with warnings. (View the details) Close this message

Error: mysql "myuser_drupal"
Unable to define superuser password for mysql server on localhost

Error: mysql "myuser_drupal"
Unable to get list of db servers (ErrorCode: 1, STDOUT.

Error: mysql "myuser_wp_eng"
Unable to define superuser password for mysql server on localhost


this repeats for every database plesk has.

How can I fix that ?

 

[ProWebS]

no one?
so it seems I'll have to pay again for a Plesk's own problem to be fixed by their support.
"nice".