I've found out what was causing my problem with this. When I installed the flyout menus the field sizes were too big for the image that I was using in each field so you saw the ugly partial repetition of the image that you see in the screenshot that comes with the download.

To fix the problem, I shrunk the size of the field.

What I didn't understand was that this introduced white-space between the fields, making it almost impossible to move from layer of category to another without the menu disappearing.

The correct fix is to add the "background-repeat: no-repeat;" instructions to your CSS. This leaves the spacing with the required overlap and gets rid of the ugly partial repetition.

Hope this helps someone else.

Possum.