Check your Season Pass for Dexter on channel 101 if you have a DirecTiVo. This is an edited replay of Showtime's season 1 of Dexter on free channel 101. The first three episodes recorded correctly. But then DirecTiVo stopped scheduling the episodes. Other discussion thread indicates a possible bug or conflict with pay-per-view in the same channel number range.
Workaround is to setup a recurring manual recording by entering the channel number and start/end times.