Sub-navigation not working on Android devices

I’m using the twenty eleven template v 1.5. On Android devices the 2nd level menus in the navigation don’t work (I can reproduce that here: http://wp-themes.com/twentyeleven).

[Link amended – Please remember to start hyperlinks with either “www” or “http://” so that these forums parse it properly]

What happens when I click (touch) on “Parent Page” is:
– the sub-menu “Sub-Page” is displayed
– the page “Parent Page” is loaded immediately
– a click on “Sub-Page” has no effect
– the sub-menu is closed without effect

Is this a known bug? Is there a workaround? I can reproduce the described behavior on my Samsung Galaxy Tab 10.1 and on my Samsung Galaxy S2 with Chrome and Firefox.

Thanks for your help.