I have been trying to download the D3 from the official site and it hasnt been working for the past 2 days and finally i just decided to go old school and try out internet explorer and it is currently downloading hope this helps see you when hell opens up!
I had this previous problem myself, and if you are installing from a browser; check the country you are downloading from. In the URL for battle.net, you should find EU, US etc. Change this to your country. It fixed my problem.