Confirmed/tested: select all "in group" and "delete" does work on VIP612.
Contrary to what primestar said above, you can and I do go into folders, then hit the edit button, then the select all button, and then delete button, and it only deletes programs within that one folder. It's when you hit Edit on the main level that you can delete everything by mistake. IMHO that option should be greyed out, or a big a$$ warning popup saying how many recordings you're about to delete. Something! Because it is all too easy to delete the whole shebang.
Despite this being an old thread, two of us in our house have three times deleted everything over the last couple years on two VIP612s. So, just getting a new replacement VIP612, I tested Feb-2013 to figure out what went down. I've confirmed, at least when working properly, selecting group "Group by Title" or "My Groups", then drilling into a group, then edit, then select all, then delete, just deleted the items in that group.
I beleive TheKrell hits it right on: that the problem is an inherent user interface flaw. Drilled into a group or not, when you move to the menu items on the right your selection on the left is gone, and things are "mentally" ambiguous. One can easily move to highlight a group on the left, then move right and pick "edit" and "
think" they are "editing" the group. Select all at that point and you've specified everything, since you had not drilled into the group, and yet one may not remember it that way. After poking around a long while, I believe this is what happened to us, though I certainly do not remember it that way, and despite having programmed computers for over 30 years such that I am almost a machine myself.
A simple "Are you sure you want to delete X items", or "delete everything on this DVR" would be nice, considering many have hit this issue, and considering "protect" only applies to auto-record and not delete (which is not intuitive). But, don't hold you breath.
Of course, it is also possible there are bugs in some unique cases.
However, the basic delete using "select all" within a group is actually implemented.