Right at the end of the hour or so of bucking I did this weekend, I had to stop and clean out the chainsaw several times since it was balking, making smoke and sparks. In fact, I had to stop just short of finishing the last cut because several rounds of cleaning hadn't helped, and the sparks were getting worrisome. So I just used a splitting wedge to finish the last cut.
Yesterday I disassembled and reassembled the chainsaw, cleaning as I went, and found no obvious problems; but the unit continues to spark and give off smoke when it's run, and the last time, it stopped running altogether. So I guess it's official, the chainsaw is down.
It's only seven months old so it's still on warranty, and I've begun the process of getting a warranty repair or replacement. It was purchased from True Value by way of Amazon, so I'm not sure exactly how to go about that. The manufacturer says to go through a nearly authorized retail outlet and I'm not sure which that is. I put in an email and if I don't hear back in a day or two I'll contact the manufacturer.