You're not the only one who sees this with the Cisco box.. I had the experience last night and it wasn't the first time. For me, it didn't happen spontaneously. I was watching real-time a program that I had previously scheduled to record. About 1 minute into the show I pressed to DVR button on the remote intending to cancel the recording. The DVR menu appeared and I selected the "recordings" list, then highlighted the program actively recording, and selected and confirmed "cancel this recording". It was then that the box objected with the same behavior you've noted. If was more than frustrating to lose about 4 minutes of the program, waiting for the box to shut down and reboot.
In retrospect, the next time I want to cancel a recording in progress, I'll try to remember to STOP the recording first, (pressing the STOP button on the remote) prior to "canceling" and see if that makes any difference. If not, I'll just wait until after the program finishes recording before deleting it. I don't think I've ever had the problem immediately after going to the DVR button before trying to do anything further.
P.S. I was told by VZ when I contacted them in mid-Oct about a problem I had with failure to record any audio at all on a scheduled recording of a PBS program (another well documented and longstanding problem noted in the VZ user's forum), that their DVR firmware was to blame and assured me that the problem would be fully resolved when they pushed a firmware update during the first week of November. It's now the second week of Nov and I still have not noticed an updated firmware version number.
If anyone from VZ monitors this board, a comment here would be GREATLY appreciated!