Setup Domain with Amazon EC2

The first thing to do in this situation is to use the -v option to ssh, so you can see what types of authentication is tried and what the result is. Does that help enlighten the situation?

In your update to your question, you mention "on another local Ubuntu". Have you copied over the ssh private key to the other machine?

First of all double posting is not very good etiquite, and making people go offsite to find your question just makes it worse. Please consider editing your question to actually be self contained here, then make SURE you update both sites with any developments and the answer once you figure it out.

Secondly, there really isn't enough information here to figure out what you've done wrong. The suggestion on the AWS forum is a good one. You seem to still be doing some things with the IP and host records from before your elastic ip was assigned. When you do that assignment your host name and ip will change! However you need to elaborate your configuration. What does your DNS look like? What domain are you trying to connect to and what does it get "forwarded to"? Are we talking about ec2 host name domains or a custom domain of your own? If the former you are just using the wrong address. If the latter your DNS records are not entered properly. They should be CNAME's to your elastic ip host name so that proper internal vs external addresses are returned.