DISTRACTED BY AN APPARENTLY UNASSOCIATED NAV SYSTEM PROBLEM; FLT CREW OF A300 FAILS TO DISARM THE EGPWS SYSTEM AS REQUIRED BY A SECOND ANOMALY; A FLT POS DISAGREE ECAM WARNING. THE COMBINED NAV ISSUE AND THE STILL ENGAGED EGPWS RESULTS IN AN ANOMALOUS TERRAIN WARNING ON FINAL APCH IN VMC.

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APCHING THE TOP OF DSCNT; WE GOT AN ECAM MESSAGE: 'NAV/ADC; FM/GPS POS DISAGREEMENT.' WHILE RUNNING THE POS DISAGREEMENT CHKLIST; WE DETERMINED THAT OUR POS WAS APPROX 200 MI AWAY FROM WHERE THE FMC SAID WE WERE. SO OUR NAV SYS WAS LOST AND WE ADVISED ATC. WHEN WE DID SO; THEY GAVE US CLRNC DIRECT TO ZZZ AND A XING RESTR OF 11000 FT 35 MI PRIOR TO ZZZ. WE BECAME OCCUPIED WITH THE IDEA OF HOW TO DO THAT IN RAW DATA. WE FIGURED IT OUT AND MADE THE XING RESTR. WE WERE NOW FACED WITH THE IDEA OF LNDG ON RWY 29 WITH A HEADWIND OF 28 KTS GUSTING TO 40 KTS. IT WAS BUMPY AND WE ONLY HAD THE LOC RAW DATA AND VECTORS WITH WHICH TO NAV. WE WERE IN CLOUDS UNTIL APPROX 1800 FT AGL. CONSEQUENTLY WE DID NOT GET BACK TO THE POS DISAGREEMENT CHKLIST AND ACCOMPLISH THE LAST ITEM WHICH WAS 'EGPWS -- OFF.' WE ACCOMPLISHED ALL OTHER CHKLISTS AND THE POS DISAGREEMENT CHKLIST WITH THE EXCEPTION OF THAT LAST ITEM. ON SHORT FINAL IN VMC THE 'TOO LOW TERRAIN -- PULL UP' WARNING WENT OFF. WE KNEW WHY IT WAS GOING OFF; BECAUSE THE AIRPLANE THOUGHT IT WAS 200 MI BEHIND US. WE HAD A CLR VISUAL OF THE RWY AND WERE CLEARLY IN A POS TO LAND. WE BOTH AGREED TO IGNORE THE EGPWS AND LAND. LNDG WAS UNEVENTFUL. THE ONLY THING I CAN THINK OF THAT WOULD HAVE PREVENTED THE MISTAKE OF NOT FINISHING THAT CHKLIST IS TO HAVE REALIZED THAT WE DID NOT CALL THE POS DISAGREEMENT CHKLIST COMPLETE. HAD I REALIZED THAT THEN; WE WOULD HAVE PROBABLY GONE BACK TO THE CHKLIST AND FOUND THE LAST ITEM.