[Typo3] Blank edit page for regular user

[Carsten Gehling]

I have met some really strange behavior in Typo3 version 3.8.0. To further
explain it, I've made some screenshots - see the links.

I have made a fresh install of Typo3 with the "dummy" package. As admin,
I've created a single page:
see http://www.gehling.dk/typo3/1.png

After this I've created a group and a user ("andre"), who gets as his
db-mount the page created above.
see http://www.gehling.dk/typo3/2.png and http://www.gehling.dk/typo3/3.png

I have also made sure, that andre's group is set as "group-owner" for the
page.
see http://www.gehling.dk/typo3/4.png

Now I log in as "andre". I can see the db-mount as my first (and only page).
BUT when I try to create a content element or create a new page, I just get
a blank frame, with no edit-form.
see http://www.gehling.dk/typo3/5.png

What have I done wrong/forgot?

- Carsten