Have you tried providing a traceroute to Blizzard in the Technical Support Forum?
Currently, they are having issues with players that have Comcast internet service. You may or may not be one of those affected.
You would probably be better assisted in this forum here.http://us.battle.net/d3/en/forum/5386227/
This thread might provide a little more details if you're in the Seattle area.http://us.battle.net/d3/en/forum/topic/9377319740
Based on what little information has been provided, I cannot offer any assistance beyond this. =(
If you do not know how to provide a traceroute, this article may be of some assitance.https://us.battle.net/support/en/article/performing-a-traceroute
For example, if you are running Windows, you will need to go to Start > Accessories > Command Prompt (Or hit run and type "CMD")
When you are in the command prompt, enter the following based on what region you are trying to log in to.
tracert 220.127.116.11 > c:\tracert.txt
tracert 18.104.22.168 > c:\tracert.txt
tracert 22.214.171.124 > c:\tracert.txt
You will then need to make a post in the Technical Support copying and pasting the information from "c:\tracert.txt"