As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT FL 340, THE VTK FLAG APPEARED ON CAPTAIN`S NAVIGATION DISPLAY WITH SIMULTANEOUS BLANKING OF BOTH FMC DISPLAYS. RAN FMC FAIL QRH CHECKLIST TO RESUME NORMAL OPS. ACFT GROUNDED. KNOWN ISSUE WITH U11.0 SOFTWARE. VERIFIED BOTH FMCS ONLINE AND OPS NORMAL. NO FAULTS FOUND ON FMC BITE CHECK, IAW FIM 34-61 TASK 837 AND FIM 34-61 TASK 801.