What was found
AIRCRAFT NOT GROUNDED: PILOT REPORTS DURING CRUISE, LNAV AND VNAV BOTH DISCONNECTED, FOLLOWED BY VTK AMBER ANNUNC ON F/OS NAV DISPLAY. BOTH SIDES LOST RTE INFO. COULD NOT SELECT ANY DIRECT WYPTS. COULD NOT SELECT INIT REF PAGE. F/OS FMC MOMENTARILY DISPLAYED SINGLE FMC OPERATION. BOTH FMCS WERE LOCKED UP. BOTH FMCS RETURNED, THEN FAILED AGAIN (SAME SYMPTOMS) THEN BOTH FMCS LATER BECAME OPERABLE, REMAINED SO FOR BALANCE OF FLIGHT, AFTER RELOADING ALL INFO. MAINTENANCE ACCOMPLISHED FIM TASK 34-61-00-810-801. FMC 1& 2 BITE PASSED.