What was found
IN CRUISE FLIGHT APPROACHING THE CRITICAL POINT ON OUR ETOPS FLIGHT PLAN THE CAPTAINS SIDE NAV DISPLAY SHOWED VTK FLAG FOLLOWED BY A MAP FLAG ALONG WITH FMC P/RST CAUTION AND NO FMC DATA ON BOTH CDU'S AFTER ABOUT 30 SECONDS THE LEFT FMC RESET ITSELF AND CAME BACK ONLINE. NORMAL NAV DISPLAY FOLLOWED. GROUNDED - YES. FAULT LOGGED WAS " PRES POS LAT-RATE" ACCOMPLISHED B737-900 FIM 34-61 TASK 824/34-61 TASK 801, ADIRS SHOW NO FAULTS LOGGED AND GROUND TEST OK REFERENCE FIM 34-21 TASK 801 NO CURRENT DISCREPANCIES NOTED.