Blizzard Download: This download is not authorized

I'm on Windows 7. When I download Starcraft Anthology from the website and try to install it on my computer I get the error "This download is not Authorized" followed by "There was a problem authenticating your download. Please go to http://www.blizzard.com/account/ to start a new download."

I've tried Safe mode, and running it as administrator, and both at the same time. I tried downloading it in Safe Mode with Networking on Internet Explorer. I have tried redownloading the downloader. There's a timestamp encryption on it, so you can only use it the day you download it.

I have tried downloading it to a different folder. Both running the file from another folder, other than where it is currently, and extracting it to another folder than the one specified. I tried deleting the following registry key:

HKEY_CURRENT_USE​R\Software\Blizzard Entertainment\Downlo​ader\ 

I get the error "This download is not Authorized" followed by "There was a problem authenticating your download. Please go to http://www.blizzard.com/account/ to start a new download."

Googled references:

Battle.net Forum -Diablo 3 Not authorized
Battle.net Forum - Starcraft 2 Beta
Battle.net Forum - Diablo 2
Battle.net Forum - Starcraft 2
Battle.net Forum - Warcraft 3 + Addon
Battle.net Forum --Starcraft Anthology
Starcraft EU - Mac Support
GamerTechTv - Blizzard Download issue
WoW Blue - Error 3.3.3 not authorized

Solution 1:

I was having this problem with my legacy games downloads. I managed to make it work by keeping Internet Explorer open during the download.