That is weird! Only "reason" I can think of is that someone pressed the "record" button twice while watching the Olympics and it set up a SL for the default SL.jmdaniel said:
Couple that with the way NBC, et. al. are blocking their shows and I can easily see how that could fill the user portion of the drive. NBC has the shows blocked at up to 8 hour increments (IIRC) and 5 of those if you are using OTA in MPEG2 could come close to filling the drive.
Hope you can remember some of the shows you lost and can find them on the web (although I abhor TV on a computer, personally, I will do that, in an emergency.)