That's all i really wanted to say. Seems like a bug to me. I found out the annoying way when going back to the begging of my camera layer and noticed it was all messed up only to discover that the POI had suddenly became active. I confirmed the "bug" by opening a new comp and trying the same thing - create key framed animation with one node camera, hit the reset button, and it becomes a two node camera.
Um, not really following that "node" thing. Do you mean "node" as in parenting the camera to nulls to have a Pan contol and a Tilt control, or because the point of interest became active when you reset the camera's properties.... as it should do?
No, just the actual camera type itself. If you're still confused, click Layer > New Camera and up the upper-left part of the dialogue box when you create a new camera you can select what type you'd like it to be - Two Node or One Node. One node simply does away with the POI - point of interest. So when you reset the camera transform controls (like to put the camera back at the center position), it switches over to a two node camera. Your position key frames are sudenly affected by a static POI basically screwing up all the camera motion.