Without the full project, we're making guesses based upon previous experience.
One way of trying to fix this is to add the following line to user_routines_fast.c before any other #include directives.
Code:
#include "p18f8722.h"
Check Configure->Select Device, make sure device in dialog box is
PIC18F8722
Then do:
Project->Clean
Project->Build all
Report any errors. Are there no warnings or messages in the output before this? What is the specific error line, "'J:\*\" should be "J:\<dir1>...\" MPLAB is path length sensitive..., what is the exact error message output.
I added the defines to my project and it compiled/linked ok so it is something else either within the source files or within the build environment.