I have the Harman P61A and have had it since January. My ex also has the same stove and has had his for 4 years now. Neither of us have come across this before, but today I'm noticing some creosote (black tarry like substance) in the stove. If anyone is familiar w/ the stove I have, I can kind of describe where it is. You have the burn pot w/ the "cover" on top and behind that are the 3 bricks. It's under the 3 bricks and above the "cover" to the burn pot. I cleaned the stove 4-5 days ago and noticed it a TINY bit, but it was just behind the "cover" to the burn pot. Now, it's all along the edge underneath the bricks all the way to both sides of the stove itself. Any ideas? Should I turn my stove off and have someone come look at it? It keeps catching on fire and it's making me nervous. I forgot to add, that I am burning Westwood Premium Pellets that I got from Pelletsales.com. I've been burning them since about mid October. I ordered some for other people also and they haven't had any issues with the pellets doing this. It was really cold here yesterday, so I had the stove up pretty high (stove temp of 5-6, with feed rate of 4).