Are you compiling for the PIC18Fx431? Although the application note was written for the PIC16 chips, I used it as a guide to program a much more capable PIC18F2431 chip. The error has to do with redefining this variable:

DEFINE INTLHAND INT_ENTRY_L ' Context saving for Low Priority Ints

But not quite sure why you are getting that, without knowing more about your setup.