Pages not showing in admin

Hi all,
I am experiencing a problem with WordPress in one of my sites (https://www.laberlera.it/).

The problem is that on the admin the “Pages” section does not longer show the list of pages. Here a screenshot.

The only way I have now to modify the pages is to navigate the site, arrive on the page I want to change and click “(edit this)”.

The problem started few days ago, more or less when my hosting provided automatically upgraded my installation of WordPress from 2.9.x to 3.0 (I am on Dreamhost and they offer the service to keep any CMS they offer automatically updated).

Any idea?

Thank in advance.