B767 CREW GOT A 'TERRAIN; TERRAIN; PULL UP; PULL UP' GPWS WARNING AT 500 FT WHILE FLYING THE LOC RWY 27 APCH AT SAN.

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PRIOR TO OUR DSCNT AND APCH INTO SAN DIEGO; WE REVIEWED THE WARNING ABOUT MAP SHIFTS IN THE SAN AREA. WITH THE CAPT FLYING THE APCH; LOC RWY 27; IN MISSED APCH MODE AND ME MONITORING IN ILS MODE; WE NOTICED THAT WE WERE XING THE FIXES ON THE APCH; AS IDENTED BY LOC DME; ALMOST 2 MI PRIOR TO REACHING THE FMS WAYPOINTS. WE WERE IN VISUAL CONDITIONS THROUGHOUT THE APCH. WE BEGAN OUR DSCNT FROM THE MDA AT THE COMPUTED NORMAL DSCNT POINT; CTRED ON THE LOC COURSE WITH THE PAPI SHOWING 2 WHITE AND 2 RED. AT AROUND 500 FT AGL; WE GOT A TERRAIN 'PULL UP' WARNING FROM THE GPWS. WE CONTINUED TO LNDG. I HAD EXPERIENCED THIS ON MY PREVIOUS TRIP ON A B757. THIS WAS ON A B767. ON PREVIOUS FLT; WE WERE HIGHER ON GLIDE PATH AND NEVER GOT THE GPWS WARNING. I DID NOT OBSERVE A MAP SHIFT DURING THE APCH. THE FMS WAYPOINTS WERE INCORRECTLY COMPUTED AND/OR DISPLAYED THROUGHOUT THE APCH. THIS IS A CRITICAL SAFETY SYS AND SAN DIEGO IS A TERRAIN SENSITIVE ARPT. WE NEED TO FIX THIS PROB BEFORE IT CAUSES AN ACCIDENT.