Actually, I think the portion of my reply that you quoted may be taken out of context without the second bullet point in the original reply's content. I would have to see the update history on either or both of the problem machines in order to make a judgement call on that. As noted in my second bullet point, the only machine that I had trouble with this morning was one that was already set to 8.8.8.8 / 8.8.4.4 and I found that by first installing the optional update by itself, the problem with installing the important update was subsequently resolved.
TBH, I feel that if you have corrected the error the point is moot. I do sincerely appreciate you following up with your own experience as I don't believe that any one solution offered thus far is a one-size-fits-all solution. What seems to work for one computer's configuration does not necessarily work for another but I feel that the community's contributions are collectively helping others in similar situations.