UPDATE: I'm sorry I have't heard or seen any updates to any fixes yet (surprise surprise). BUT it's been a while since we've all heard from Gina Bruno, the admin and community manager for Zenimax Online. Here's her latest response to this thread @ https://beth.games/2pIzsJo.
"Just a quick update - we believe we've identified the issue causing this, and are working on getting it fixed as soon as possible. We'll let you know when you should be clear to install the game." - May 16th, 2017
I have been checking every 10 minutes for ANY kind of communication from Gina and her "capable" team. Nothing so now I am, for the sake of all of us, am now downloading the game again to see whether anything changes. So one of two things will happen:
The game will successfully download and there will be some head scratching because you'd expect them to communicate to us that there was a fix
The same error pops up around 20%-25% mark...hence Zenimax is still...still working on a fix after 3 days now.
I WILL LET EVERYONE KNOW SOON ENOUGH! The launcher is currently @ the 8% mark.