FLC EXPERIENCED PROBS WITH THEIR LONG RANGE NAVIGATIONAL EQUIP RESULTING IN BECOMING OFF COURSE APPROX 90 MI OVER AN OCEANIC RTE.

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THE FLT WAS IN A LEARJET MODEL 35A FROM PNE TO TNCM. THE FLT PLANS WERE DONE BY UNIVERSAL AND WE DEPARTED USING GPS AND 2 VLF OMEGAS FOR NAV TO TNCM. WHILE IN CRUISE; THE GPS WAS DISPLAYING ERRONEOUS INFO AND WE TURNED TO OUR 2 VLF OMEGAS FOR NAV. WHILE PROCEEDING SBOUND; WE TUNED IN BERMUDA VOR TO DOUBLE-CHK OUR POS. WE NOTICED OUR BEARING AND DME TO BERMUDA DID NOT AGREE WITH OUR 2 VLF OMEGAS. IT WAS AT THIS TIME WHEN WE REALIZED OUR VLF OMEGAS WERE INACCURATE! MINS LATER; COMMERCIAL RADIO ASKED US TO SWITCH OVER TO BERMUDA APCH. BERMUDA APCH ASKED US OUR POS. WE READ OUR LATITUDE AND LONGITUDES FROM OUR VLF OMEGAS AND BERMUDA CONFIRMED THAT OUR FINDINGS WERE CORRECT; THE VLF OMEGAS WERE INACCURATE. BERMUDA WAS AWARE OF OUR NAV EQUIP MALFUNCTION AND TWICE THEY GAVE US OUR LATITUDE AND LONGITUDES SO WE CAN REPROGRAM OUR VLF OMEGAS. ONCE OUR VLF OMEGA MATCHED BERMUDA'S POS ON US; WE WERE GIVEN A NEW ROUTING TO ST MAARTEN AND WE CONTINUED WITHOUT FURTHER COMPLICATIONS. BERMUDA APCH INFORMED US THAT THIS ERROR CAUSED US TO BE APPROX 90 MI E OF COURSE! NO EVASIVE ACTION WAS REQUIRED DURING THIS OCCURRENCE. CONTRIBUTING FACTORS WERE ERRONEOUS GPS AND VLF OMEGAS. (WE WERE NOT AWARE OF VLF OMEGA ERROR.) I DO NOT KNOW WHY WE RECEIVED SUCH ERRORS IN OUR SYS AS THEY HAVE WORKED WELL IN THE PAST. MY SUGGESTION TO PREVENT SUCH AN OCCURRENCE WOULD BE TO HAVE SYS STATUS AND ACCURACY CHKS PRIOR TO ANY OVERWATER FLTS WHERE NAVIGATIONAL FACILITIES ARE SPARSE.