Bruno,
Dannix code and your sample says MW_NULL not MW_null or are we talking about different things?
I had to declare MW_navbtn as int too in top section.
Now code stops at r=menu.addMenu(MW_ROOT,NULL,F("MAIN MENU")); //create a root menu at first (required)
telling no matching call to 'MENWIZ::addMenu(int,NULL,_FlashStringHelper*)'
I now about the debounce butfirst I have the four menu buttons to work.
I think the delay in the button call is enough but have to see.
Paco