WDB ACFT IN CRUISE ON OCEANIC RTE WAS OFF COURSE DUE TO EITHER A FAULTY IRS OR DATABASE ERRORS. WAYPOINTS WERE IN ERROR AND RPTR CAPT CLAIMS THAT CORRECT ENTRIES HAD BEEN MADE BEFORE FLT.

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ENRTE FROM LONDON HEATHROW (LHR) TO NEW YORK (JFK) WE WERE CLRED DIRECT TO MERLY INTXN. ABOUT 50 MI NE OF MERLY WE WERE CLRED TO N52W15 DIRECT. WE ENTERED THIS WAYPOINT FROM THE DIRECT INTERCEPT PAGE OF THE FMC; BOTH PLTS VERIFIED AND THEN EXECUTED THE PAGE. WE PROCEEDED TO 15W AND ABOUT 3/4 OF THE WAY THERE THE ACTIVE WAYPOINT BEGAN TO APPEAR AS N52W104 ON THE FMC AND THE HSI. SHORTLY THEREAFTER; ATC (SHANNON) CONTACTED US ON VHF AND TOLD US TO FLY A HDG OF 180 DEGS. ORIGINALLY; WE THOUGHT THE TURN WAS FOR TFC (WE WERE STILL IN RADAR CONTACT). I QUESTIONED THE CTLR AND ASKED HIM HOW LONG WE WOULD BE ON THAT HDG. HE TOLD US THAT HE SHOWED US 16 MI N OF COURSE. WE LOOKED AT THE FMC AND SAW THE ACTIVE WAYPOINT AS N52W104. IT SHOULD HAVE BEEN N52W15. NEITHER MYSELF NOR THE FO HAD ENTERED THAT WAYPOINT AT ANY TIME. THE FMC RTE WAS LOADED BY ACARS DATA LINK IN LHR. ALL COMPANY SOP'S WERE FOLLOWED AND THE RTE VERIFIED BY BOTH PLTS. THE ONLY THING THAT WAS NOT ACCOMPLISHED WAS A LINE SELECT AND COORDINATE VERIFICATION OF THE ABBREVIATED OCEANIC WAYPOINTS WHICH IS NOT REQUIRED UNDER OUR SOP'S. ONCE WE CORRECTED BACK TO COURSE WE REVERIFIED THE WAYPOINTS IN THE FMC'S. WE DISCOVERED THAT THE NEXT CHKPOINT LOADED (N52W020) WAS ALSO WRONG. WHEN WE LINE SELECTED IT DOWN THE COORDINATES WERE WRONG SHOWING AS N5217.8W020. ADDITIONALLY ANOTHER WAYPOINT WAS ON THE LEGS PAGE THAT WE DID NOT ENTER. WE DELETED THIS PHANTOM WAYPOINT AND RE-ENTERED THE COORDINATES OF THE SUBSEQUENT OCEANIC WAYPOINTS SPECIFIED IN NAT TRACK E; OUR CLRED RTE. AFTER THE EVENT WE SUSPECTED BAD DATA ON THE FMC DOWNLINK OF THE RTE. DISPATCH WAS NOTIFIED. AT NO TIME WAS THERE A LOSS OF TFC SEPARATION; AND BECAUSE WE WERE STILL IN RADAR CONTACT WHEN WE WENT OFF COURSE; NO OCEANIC GROSS NAV ERROR OCCURRED. LATER IN THE FLT WE GOT A R IRS FAULT ERROR. THE IRS WAS OPERATED IN ATTITUDE ONLY AND NAV WAS NORMAL. THE R IRS WAS ALSO SUSPECTED AS A CONTRIBUTING FACTOR.