We had purchsed 4 Kitchen Aid microwaves (Model KCMS1555RSS-1) in Feb. 06. Approximately, 6 mo. ago, one of the units malfunctioned (Serial # FGS3006428), in the off mode- the unit remained on and started smoking. The light and turn-table inside remained on while unit smoked/caught fire. We had to unplug machine. Last week, a second unit(FGS3006313) did the same thing. I called Kitchen Aid to report defect unit and they sent tech. to diagnosis problem. He said the transformer had caught fire. He noted he never seen that happen before and in his opinion thought the motherboard (computer) has caused this to happen. I just got off phone with Kitchen Aid and they seem uninterested in the safety hazard these machines may cause. I spoke with Jim Cuhn, Safety Lead at Kitchen Aid/Whirlpool. Kitchen Aid has refused to stand behind their product (denied request to further invetigate/repair our machines) and I am concerned that other uses of this model may experience fire due to this product.