Good thought, 4est. I don't think I was, but I'm pretty sure the USB connection was there and idle. Also, it would not be unlike me to do something else while it rips, but in this case, I've tried the same CD several times without doing anything else so it's definitely no that. In the case of the tower that ripped it successfully with no artifacts, there was definitely no output device connected, and nothing else processing while it was ripping. I will certainly post anything I learn here. Thanks for the input thus far.
Marco