FO OF AN WDB MISSED PROGRAMMED A FIX IN THE INS NAV UNITS CAUSING AN OFF COURSE N ATLANTIC TRACK OF 60 MI.

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FO LOADED 49N 50W INSTEAD OF 48N 50W IN ALL 3 INS UNITS USING REMOTE LOADING WITH #2 AS MASTER WHILE AT THE GATE AT ORY (PARIS ORLY). WE CHKED THE WAYPOINTS WITH MY READING THE COORDINATES FROM THE #1 INS WITH THE FO CONFIRMING EACH ONE. HE FAILED TO NOTE THE ERROR. AFTER XING 40W THE FO NOTED THAT THE #2 INS WHICH WAS IN TRIPLE MIX AND COUPLED TO THE #2 AUTOPLT HAD A FLASHING 'E' WHERE IT NORMALLY HAS A 'U' WHEN IN TRIPLE MIX. THE E AND U WOULD ALTERNATE APPEARING ON THE #2 UNIT. WE SPENT CONSIDERABLE TIME TRYING TO DETERMINE WHAT THIS MEANT AND HOW IT WAS AFFECTING OUR TRACK. THIS IS THE TIME THAT I NORMALLY PLOT OUR POS. I SOMEHOW MENTALLY SUBSTITUTED CHKING THE INS UNITS FOR THE PLOTTING I ALWAYS DO WITHOUT FAIL. THEN ABOUT THE TIME THE UNIT (#2 INS) STARTED OPERATING NORMALLY WE ENCOUNTERED MODERATE TURB. I MADE 3 RADIO RPTS TO OTHER ACFT ABOUT THE TURB. GANDER CTL TOLD US WE HAD PASSED OVER 49N 50W INSTEAD OF 48N 50W. THERE HAD BEEN NO CONFLICT WITH TFC; BUT SINCE WE WERE 60 MI N OF COURSE AND ON THE WRONG NAT TRACK THE POTENTIAL WAS ALL TOO CLR. I ALLOWED A DISTR TO AFFECT MY NORMAL PROCS; AND IT WAS AT A CRITICAL TIME. I'M FULLY AWARE THAT MISTAKES ARE MADE; BUT THAT PROCS; IF FOLLOWED; WILL CATCH MOST OF THEM.