[Q] Can't access 'more' menus?

I just got a Shield at the weekend, and I'm loving it apart from a rather annoying snag that I have come across.

When I call up the menu within an app, I get the usual bar along the bottom of the screen showing various options.
Usually, the rightmost option is 'more', which brings up a sub menu with further options.

For some reason, I can't select any of the options in the 'more' menus on any of my apps.
I have tried using the buttons, the touch screen, and the mouse pointer, but none of them will highlight or select options.

This is close to a disaster, because most of my apps have something important hidden away in the submenus, and I can't use them properly on my Shield.

I'm using some of these same apps on my Xperia Play, and they work fine.

Have I got a setting wrong or something, or is this a bug in the Shield firmware?

EDIT:

False alarm!
I thought my Shield was up to date, but I guess it wasn't.
Updated Android, and the menus are working fine now.