MENWIZ: yet another character lcd menu wizard library

I had this same problem and found that my copy of the menwiz.h library was different on the other computer. I usually copy my files onto a usb drive to move them between computers. I somehow managed to get a copy that did not have the #define BUTTON_SUPPORT line commented out. So if you don't have #include <buttons.h> in your sketch and the menwiz.h calls for it you get the error.