Still had this problem attempting to install last week; I finally got around it by right clicking on the Turbotax download file, selecting 'run as administrator', and then when the install process asks where to put turbotax choose a directory different from 'c:\Program Files'. I would guess pretty much anywhere else under c: should work.
The resulting install seems to work normally, but this is the first time the install location has mattered for Turbotax in 15 years of my using it. None of the workarounds I've found online for this issue actually made a difference for me, so I hope everyone can waste less time than I did fixing this problem.
