As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF THE CREW REPORTED THAT THE COMM 2 RMU WAS BLANKED OUT AND THE BACK-UP HEAD COULD NOT BE TUNED AND THAT COMM 1 WAS SWITCHING BETWEEN ACTIVE AND TUNING FREQUENCIES. THE AIRCRAFT RETURNED TO IAH AND LANDED WITHOUT INCIDENT. MAINTENANCE TROUBLESHOT THE FAULT TO THE RMU 2 AND PLACED IT ON MEL. THE MEL WAS CLEARED IN CMH ON 1/4/2011 WHEN MAINTENANCE CLEANED THE CONNECTOR FOR THE NR 2 RMU AND THEN RE-SECURED THE CONNECTOR WITH NO FURTHER DEFECTS NOTED.