I couldn't really find this problem / resolution in the forums so I thought I would contribute for those who might have the same issue.
I recently noticed that my Media Center PC was on (not sleeping) almost all the time lately. Not only was it on, it was running at full speed and the fans were coming on. After some investigation I found that ShowAnalyzer was processing 3 older files that should have been processed already. Once it was done it proceeded to process them again and again. The processing doesn't go well either; there's a stall part way through. When I looked at the logs for these files I found the same thing over and over again:
Finished Commercial Detectection