What was found
CLT - FLT 667, EN ROUTE CLT TO LAS - AFTER TAKEOFF, RECEIVED AN EICAS MESSAGE "GEAR DOOR" WITH THE LANDING GEAR HANDLE UP. ALSO, RECEIVED AN AMBER "DOORS" LIGHT. THE GEAR LIGHT AND ALL THREE GREEN DOWN AND LOCKED LIGHTS EXTINGUISHED. THE CREW CYCLED THE GEAR, BUT STILL HAD THE SAME INDICATIONS. THE FLT RETURNED TO FIELD AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE PERFORMED TROUBLESHOOTING PROCEDURES AND NUMEROUS GEAR SWINGS. THE FAULT COULD NOT BE DUPLICATED. OPERATIONALLY CHECKS OK.