[TYPO3] Page tree empty after 4.2 upgrade

[Dreas van Donselaar]

I upgraded our development server to Typo3 version 4.2. For some reason 
the page tree only shows the root (ID 0) page. All my other pages are 
not listed so I cannot edit them.

Any idea why this is occurring and how to solve it?

Kind regards,

Dreas