Thanks for looking gman... like I said, this is the first time it happened, so I wonder if maybe the sleep timer went just as a frame finished and the CPU dropped? But that shouldn't do it... I'm puzzled myself.

One other time, I came home to find that the batch render had quit partway through. I was a windy day, and although the power hadn't gone out, I wondered if there might have been a brown out or something? Don't know if that would cause it... weird again. Seems that I should just keep tabs on my computer without any assumptions.

Sorry for the thread hijack...