pulldown menu invisible while documents 'bar' open

• The admin or author user logs in.
• He clicks on the folder button in the left vertical navigation bar.

• The content screen is shown with the documents tab open, i.e. the subfolders of it are visible.
  !* The pulldown menu for content specific actions is invisible, although the user has permission for those actions.

• The admin or author clicks on the documents tab.

• The pulldown menu appears.

So clicking on the already open documents tab, brings the CMS in a different state. That should not be the case.