I know it seems a bit unlikely, but what browser are you using for your download?
My failures were downloaded using Internet Explorer, but todays one, which worked, was downloaded using Firefox.
The Adobe guy ran my system using his remote desktop and was jumping around quite fast, but I did notice at one stage there was a file dialog which needed to be "unlocked" by checking a dialog box (that was within Windows, not Adobe).
The file that we eventually installed correctly was the one I downloaded today using Firefox.
When I asked him if the browser would have any effect he said it was unlikely but it might be possible.