Looks like I found an explanation, under the Dish Website topic of Digital Rights Management I found the following:-
Quote
Premium Movie Packages with PocketDISH and External Hard Drives
HBO® and Cinemax® are requiring DISH Network to improve the security of their movies to prevent unauthorized copies. As a result, DISH Network has recently added some copy protection to HBO and Cinemax services.
The new content protection policies will impact customers that own a PocketDISH whereby content recorded on the DVR will be moved, opposed to copied, to the PocketDISH. Once these events are moved to your PocketDISH, they will no longer be available to view from your hard drive on your receiver. Additionally, the movie or content cannot be moved back to the DVR. If these policies apply to the content you wish to move, you will be advised by a pop-up at the time of download.
External hard drives must comply with copy protection standards to be utilized to store content. If your external hard drive does not comply, you will not be able to move the affected content.
End quote
Since all my issues were with programs copied from MAX channels, I guess this answers my question. I am glad I have let my CineMAX subscription expire!!
Also in case it is an issue, my current software version is L623.
Thanks to all who responded.
Cheers