TYPO3 Core

When I'm logged in as an admin-BE-user, I cannot edit my own user's settings in User Tools -> User Settings

Entering a name or email address into the input fields and saving, the entered data is lost
Choosing a language from the dropdown and saving, the chosen language is lost

Entering a name or email into the corresponding field directly in the database and loading the form in BE: the entered data is availabld (altough changing it via the BE form fails).

Chosing a language by setting it directly in the serialized array of the UC field directly in the database, the language shown is still the default language (but maybe that's a problem of the manual changes in the serialized array).

Modifiying and saving changes to other record types (e.g. tt_content) work without problems.