As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FL 350 - AT TOP OF DESCENT LEFT FMC FAILED FOLLOWED SHORTLY AFTER BY THE RIGHT FMC. BOTH FMCS FAILED FOR ABOUT 10 TO 15 MINUTES AND THEN BOTH FMC'S CAME BACK ONLINE. GROUNDED - YES. PERFORMED B737-900 FIM 34-61 TASK 836 NO DEFECTS NOTED BOTH FMC'S RESET.