Interesting. What was the source device you were recording from? If it was an HD cable box with a 1394/DTCP output (an option on most HD cable boxes, but not selected by most MSOs), it could well be a cable-system screw-up.
If it was OTA, something's funky--no OTA programming should contain CCI (copy control information).
BTW, I'm nitpicking but, you can't record 24 in HD, since it's not broadcast in HD. It's Fox's widescreen 480p. The HD formats are 1280x720p or higher.
-- Mike Scott