That program was written with old MENWIZ library 1.1 that was supporting the 4 and 6 buttons. The new version of MENWIZ support only 6 buttons so change the lines
menu.addUsrNav(navMenu,6);
and remove or comment this line:
MW_navbtn=4;
The rest is variable declaration problem, tempF variable should be global and defined at the top above Setup();
post the total sketch here.