Changing password for user via administration page doesn't work

Subscribing a new user at .../mypads/?/subscribe creates the user in the mysql DB having i.a. an object with fields salt and hash. Login with this username and this password works fine.

Now, login as admin at .../mypads/?/admin, selecting the forementioned user and change its password one cannot login this user with the new set password. Looking in the DB the password filed in the value of key mypads:user:... is no more an object with salt and hash for pasword but a simple string as value for password. Maybe that's the problem (the missing password object).

As a workaround, can I delete a user and subscribe her anew ? Does this affect any history on existing pads associated with this user?