What was found
APPROXIMATELY 4.5 HOURS INTO FLT, AT CRUISE ALT 370, CAPTAIN LOST MAP INDICATION WITH VTK, FOLLOWED BY F/O VTK, SEPARATELY THEN SIMULTANEOUSLY, THEN ALL ERRORS CLEARED AFTER ABOUT 90 SECONDS. WITHOUT PILOT ACTION. REOCCURRED APPROXIMATELY 45 MINUTES LATER. ACFT GROUNDED. PERFORMED FMC BITE IAW FIM 34-51 TASK 801. FOUND BOTH FMC LOGGED PGM FAULT, NO OTHER FAULTS NOTED. PERFORMED FIM 34-61 TASK 807 RESET BOTH FMC CIRCUIT BREKARS, BOTH FMC REBOOTED NORMALLY FAULT DETERMINED TO BE INTERMITTENT. AIRCRAFT OK FOR SERVICE.