Delete DVR (Delete a group at once, instead of one at a time)

using the remote -

List-

Manage Recording-

Series Manger-

Page down to the series you want to delete-

Press record and follow the on screen to delete 

If you want to prevent future recordings, delete in series manager.  If you want a whole series deleted from the playlist, go to list, highlight the series but don't select it, press the plain red button on your remote.