What was found
JUST AFTER LEVEL OFF AT FL410, VNAV DISENGAGED AND A/T THRUST MODE SHOWED IN CLB MOVE. VNAV WOULD NOT REENGAGE AT ANY POINT IN FLIGHT. FMC SEEMED TO BE STUCK IN CLB MODE. GROUNDED-YES. INITIALLY COULD NOT GET INTO DFCS BITE AND THROTTLE TEST WAS FAILING. RE-RERACKED FCC A AND EVERYTHING STARTED WORKING. FCC'S TEST GOOD, IAW B737-800 AMM 22-11-33-400-801. AIRCRAFT IS AUTOLAND AND HGS CAT III QUALIFIED. AUTOTHROTTLE TESTS GOOD, IAW AMM 22-31-00-710-801.