Clifford Car Alarm, not disarming/arming HELP!?

Hi, my friend has a Cliiford Concept 500 alarm on his Focus. The remotes stopped working today! They sometimes will work but only very rarely! I have checked the batt voltage and all seems well! Does any one have any ideas? this is puzzling me and my friend needs the car for work! at the moment he cant start the car or gain entry! PLEASE HELP! Thanks Matt