Quick update everyone currently receiving an Error 3007:
We've researched your reports quite thoroughly, and the issue appears to be occurring on the ISP side and not with our game or authentication servers, which means there's not much we can do to assist with this particular problem. It should be resolved once the ISP is able to get correct DNS propagating.
In the meantime, you can try to use different DNS servers, and Narull has provided an excellent workaround for that process here: http://us.battle.net/d3/en/forum/topic/7393109275?page=9#171
Thanks again for your reports! We really appreciate players bringing this issue to our attention so quickly. (And thanks for being patient while we investigated.)
Thx for the update and the workaround link!