I'm trying to replace some regular outlets in a kitchen with GFCI's. The old outlets are combo switch/receptacle outlets, so the new ones are of the same type. The "left" one has the switch for the light over the sink and also is the feed the "right" receptacle. The "right" one is also the feed to the garbage disposal and dishwasher. With nothing being connected to the "right" outlet at all, when I connect the "hot" wire to the new GFCI on the left, the receptacle trips immediately. The house is an older one because only half of the house has ground wires and those are on the neutral bar. I've been doing electrical work for 23 years and have never come across this problem. Does anybody have any ideas> Thanks.