As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
JUST PRIOR TO LEVEL OFF AT FL330 "VTK" APPEARED ON NAV DISPLAYS. BOTH "FMC" PROMPTS ON FMC CDU MENU PAGE DISAPPEARED NAV DATA ON MAP DISPLAYS DISAPPEARED BLANKING WAS BRIEF (10-20 SECS MAX) A/C REMAINED IN L NAV AND VNAV FMCS RETURNED TO FUNCTIONALITY W/O PILOT ACTION. GROUNDED - YES. CYCLED POWER TO BOTH FMC OPS RESTORED NO FAULTS REF B737-9 IFIM 34-61-00-810-918.