[TYPO3] Empty fields in backend edit-screen after 4.2.0 upgrade

[Martin Seebach]

Hi,

After upgrading to TYPO3 4.2.0, I can no longer edit records in the 
backend. Using the list-module, I can easily find e.g. a frontend user, 
but when I click "edit", I get a screen where every field is empty.

This includes the "Username" field, even tough the username is shown at 
the top of the page.

Screenshot: http://www.martinseebach.dk/files/empty-fields.png

What's wrong?

Regards,
Martin Seebach