Background color does not change for menu items in current state

I'm using WP 3.0.1 and Atahualpha 3.5.5. Header area configuration is "%logo %pages %bar1 %image %bar2".

I created a custom menu (under Appearance/Menu in WP admin page) that contains mixed pages and categories, some with subpages.

Here is the problem: background color changes to "current state" color (same as "hover" color") only for menu items that are actual pages, not for those that are categories. Even with pages, color background does not change if the page at the top contains subpages.

See example HERE. Color changes to current state for HOME and RESEARCH (i.e. single pages without subpages) but not for say FUNDING (a category page) or for ABOUT (a "page" page with a subpage underneath).

This should not be like this, or?

Many thanks in advance!