As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LGA - FLT 950 - AFTER TAKEOFF FROM LGA, FLIGHT EXPERIENCED AN FMC PROBLEM. FAILURE OF NAV AND AIRCRAFT DATA OCCURRED. FLIGHT RETURNED TO FIELD AT LGA AND LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE REMOVED AND REPLACED THE FLIGHT MANAGEMENT COMPUTER. LOADED NAV DATA. BITE CHECKED AND OPERATIONAL CHECK GOOD. (X)