What was found
(CAN) THE ACFT DISPLAYED FMS 1 FAIL AND FMS 2 FAIL CAS MESSAGES AND RED FMS FLAGS ON THE ASSOCIATED PRIMARY FLIGHT DISPLAYS AND MAPS. ACFT RETURN TO DEPARTURE, PASSENGERS ON BOARD, DUE TO THE FMS 1 & FMS 2 FAIL RE-OCCURRING ONCE MORE IN FLIGHT. THE FLIGHT CREW WAS UNABLE TO RESOLVE THE FMS FAILURE DURING THE FLIGHT. THE FMS FAILURE CONDITION NO LONGER PRESENTED ITSELF WHEN THE ACFT WAS POWERED OFF AND POWERED ON AFTER LANDING. FURTHER INVESTIGATION SHOWED THAT REPORTED FMS FAILURE OCCURRED WHILE DEFINING A 999.99 NM IN DISTANCE CROSSING, DIST CROSS, FIX FROM THE FIX DIALOG BOX DURING A FLIGHT WITH THE DU IN MAP MODE. ISSUE INVESTIGATED AND MFG RELEASED ADVISORY WIRE AW700-34-0466 TO THE FLEET DESCRIBING THE CONDITION WITH ASSOCIATED WORK AROUND PROCEDURE. THE CONDITION WILL BE CORRECTED IN THE UPCOMING V5 SOFTWARE UPDATE.