Hello maacruz,
Thanks for the reply.
The problem I'm facing is that once I get into fullscreen mode, the fullscreen button disappears, and so does the menu. Tapping on the lower right corner does not bring up the button as is normal - thus there's no way to come out of fullscreen, except by doing a Ctrl-Backspace and quitting the zim window.

Any thoughts...
(I'm attaching a screenshot. btw I'm using n900.)