No dropdown unless top primary menu item is selected?

Hi - thankyou for are interesting theme :)

I have a menu item, its the first page of a book. The sub menu items are sup pages of that book.

My problem is, that the dropdown menu is not automatically expanded when hovering over the top menu item (se attached screenshot) - just the tooltip is shown. Only when the top menu item is selected, i can get the menu to dropdown by hovering.

Testet in IE7 and FF3

Is this by design, a bug, or am i doing anything wrong?

Best regards
Bjarne