DVR can record shows on eSATA drive, but not play them back

I recently added a 2TB disk to my Scientific Atlanta DVR.  It seemed to add the disk properly, going through the formatting steps, and then the joy of seeing my almost-full disk expanded to 80% free!  I started to record shows on the new disk, but I can't play them back.  I have several symptoms:

I select a recorded show and the small menu pops up.  Play is greyed out.

I select a recorded show and the small menu pops up.  Play is available.  I select Play.  The screen goes black except for the progress bar at the bottom, which shows the durration, such as 0:00 to 1:00.  Nothing happens.  I push pause and play, but never leave 0:00.

I select a recorded show and the small menu pops up.  Play is available.  I select Play.  I get an error message window that says the drive isn't available and to check the cables.

Any ideas?

I'd appreciate any help.