Are you sure the batteries are draining? Are you testing the batteries with a millimeter to make sure that they are dead? Lithium cells are able to last as long as 5 years or more if your getting constant checksum errors I would check the condition of the battery cradle for bad contacts, or cold solder joints, or it may even be a bad CMOS EPROM. Three CMOS batteries in less then a month is not even close to normal.