Do you live next to area 51 or some other military installation? Any new cell towers or other towers around? Anyone with a ham radio around? Anyone put in a new cordless phone or other type of tv, satelite, or computer network system with a relay by radio waves? Got any cops living nearby with police radios in their house or car parked outside? Any recent lightning strikes? Any power surges or loose neutral connections on the utility power transformers serving these houses?
Other than that, try new batteries and unplug the opener for 5 minutes or so to allow it to reset itself and ground it while unplugged to discharge any static electricity buildup in it.