This process means that you must re-download all of Diablo III again (8.19 GB) but it does work and at least there is still time before launch.
NOTE: I did follow all of Blizzards instructions to try and fix the pre-installer download but none of them worked. This is the only thing that worked for me, so don't be afraid to try Blizzards fixes first. I had .part files but the pre-installer would not fix them up. It would just start the installation and fail.
EDIT: Just finished downloading with the release installer and it all went great. Could launch D3 watch the opening cinematic and login (though Battle.net is not accepting D3 logins atm of course).