1. If the clienregistry.blob fix or changing download location doesn't work, this is for you.
2. Go to your Steam folder and back up your "steamapps" folder (Default: C:\Program Files\Steam)
3. Uninstall Steam, download it again and re-install it.
4. Put the "steamapps" folder back into your Steam folder.
5. Start Steam and download your game.
Worked for me twice ~
Btw when you change Steam to the Beta "edition" you get the bug again.