Media Center Recording On It's Own

I have scheduled and recorded two TV shows with Media Center. On both
occasions (seperate channels), about a week after I made the recording,
Media Center recorded the same show on the same channel. I did not schedule
a second recording of either and I did not have any series recordings set
up. In fact, after the first instance of this happening, I made sure that I
did not have any recordings scheduled.

Has this ever happened to anyone before?