ACR WDB FLC HAD AN FMC PROBLEM RIGHT AFTER TKOF THAT CAUSED THEM TO BE OFF TRACK ON DEP. ATC GAVE THE ACFT A VECTOR AND THE FMS CAME BACK TO LIFE.

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WE DEPARTED RWY 31L AT JFK ON THE KENNEDY 5 DEP BREEZY POINT CLB. AFTER TKOF; I CALLED FOR 'DIRECT INTERCEPT; LNAV' TO CRI VOR. BEING CLOSE TO CRI PLUS THE SLOWER COMPUTER IN THE X FMS; RESULTED IN THE APPEARANCE OF SUBSEQUENT MAP SHIFTING. WE WERE CONCERNED WITH ENCROACHING ON THE CRI 039 DEG RADIAL AND TURNED TO A 220 DEG HDG. BY THE TIME WE RE-ORIENTED OURSELVES TO BASIC VOR NAV; WE FOUND OURSELVES 2 MI S OF CRI VOR. ATC QUERIED AND ASSIGNED A 260 DEG HDG TO INTERCEPT THE CRI 223 DEG RADIAL OUTBOUND. QUITE FRANKLY; I'M NOT QUITE SURE HOW TO PREVENT THESE KINDS OF SITUATIONS DUE TO THE MANY ANOMALIES AND COMPLEXITY OF THE OP. THE ANSWER MAY BE TO GO BACK TO BASIC NAV IN THE TERMINAL ENVIRONMENT AND USE THE FMS ONCE ESTABLISHED ENRTE. IN MY OPINION; THE WHOLE CONCEPT OF GLASS COCKPIT FLYING LOOKS A WHOLE LOT BETTER ON PAPER THAN IT DOES OPERATIONALLY. NOTE: A POSSIBLE EXPLANATION TO THE MAP SHIFT ANOMALY DESCRIBED ABOVE IS THE VOR-DME UPDATING THAT OCCURS AFTER THE ACFT BECOMES AIRBORNE. AGAIN; PERHAPS BASIC NAV IS THE ANSWER. (THIS WAS EXPLAINED TO ME AFTER THE FACT). SUPPLEMENTAL INFO FROM ACN 208260: UPON LEAVING 500 FT AGL FO; WHO WAS FLYING; CALLED FOR LNAV DIRECT TO CRI VOR. I THEN SELECTED AND EXECUTED FMC TO THE CALLED FOR PROC. THE SCREEN THEN WENT BLANK FOR APPROX 10 SECONDS AND THEN SAID STANDBY FOR ANOTHER 20 SECONDS BEFORE FINALLY GIVING THE COURSE TO CRI. BY THIS TIME; WE WERE GETTING CLOSE TO THE 036 DEG RADIAL. A HARD TURN WAS EXECUTED TO SOUTHEASTERLY HDG TO REMAIN S OF 039 DEG RADIAL WITH OUR CLOSE PROX TO CRI WE ENDED UP 2 MI S OF CRI AND WERE THEN VECTORED TO INTERCEPT THE 223 DEG RADIAL OUTBOUND. I BELIEVE OUR MISTAKE WAS NOT FLYING THE DEP PROC MANUALLY. THE X FMC IS EXTREMELY SLOW COMPARED TO THE Y WHICH WE FLY ALMOST EXCLUSIVELY. ALSO CONTRIBUTING IS THE HIGH WORKLOAD ON 2 MAN COCKPIT ON TKOF AND LNDG.