I have similar or same problem with my Panasonic NN-SD681S microwave oven was purchased around 15 months ago. We use it only for heating up / reheating and popcorn, nothing exotic. Say I have set to run for 1 min 10 secs to heat up a cup of coffee. It will run for 20-30 sec, start stuttering or stalling like a car stalling out of gas, then shut off. When it shuts off the input settings on time and power are cleared. Important, a little diamond with a vertical line through it appears flashing in the bottom right area of the display, something like this <|>. I called Panasonic technical support and they were totally unhelpful. After describing the situation as said above, he said I had to pay $7.50 for him to talk to me since the unit is out of service warranty (parts are still covered). After describing the little diamond bit I asked him what it meant and he said he was not allowed to tell me. He then told me to set the time for 5 minutes and turn on, which I did. With nothing in the microwave overn. It ran the course but I notice that left hand side / outside panel of the unit upper area was extremely hot, like scalding - I thought it would burn my hand. Common sense says if you operate the microwave oven on high power input for 5 minutes with nothing inside (to absorb the heat) it might get hot. I told him that it was really hot, and asked why we were doing this. He said he was not allowed to tell me. He gave me the name of the local (independent) service company if I had further problems. What crap customer service! Can anyone help.