What was found
FLT#771. BOS-CUN. (AIRCRAFT PERFORMED AN AIR TURN BACK TO BOS). 'AFTER FIRST ENGINE START, INFLIGHT CREW ALERTED US THAT THE CABIN CMS SCREEN WENT BLANK. WE UTILIZED THE CABIN COM RESET GUIDE, WAITED 8 MINS AND THE SYSTEM RESET AND FAULT CLEARED. ONCE AIRBORN THE CMS FAILED AND WE LOST ALL COMM FROM FLT DECK TO CABIN TO PAX; OMS FAULT CODE 4411F0033, PERFORMED ON THE GROUND RESET OF CMS CABIN CTLR PRI/SEC IAW AMP J24-00-00-10AAA-398D-A WITH NO CABIN INTERUPTIONS. NO FURTHER FAULTS NOTED. OPS TEST OK OF CABIN HANDSET FUNCTIONS IAW AMP J44-11-09-01AAA-320A-A.'