Urgent! Problem after importing from MySql 7

[Alex K.]

Hello,

After importing all databases, including system (mysqldump was --all-databases) all the user accounts report:

"Account [accountname] does not exist but it still has privileges defined for the following objects: [databasename]"

I dont mind re-creating all accounts, but i can't! when trying to create or even change the "root" account i get:

Error Saving Account


Error changing account root@%: Storage engine 'MyISAM' does not support system tables. [mysql.db]

This is urgent.

Thank you