PuTTY error: "No supported authentication methods available"

Answer

There is a bug in PuTTY that requires an extra newline character at the end of your key file.  Also, PuTTY doesn't read raw key files. It only reads its own PPK file format for the keys.  You need to use puttygen to import the raw text key file and then save it as a Putty Private Key (PPK) file.

1) From the RightScale Dashboard navigate to your private key and display it using Clouds -> [region] -> SSH Keys then click on the key that your instance is using (e.g. "default").

2) Copy the entire key into a text editor such as Notepad or vim (do not use a word processor - it needs to be a raw text editor!)

3) Make sure there is an extra line at the bottom.  That is their needs to be a newline character at the end of the file or puttygen will not be able to read the file.  So make sure the cursor in the text editor is below the last line:

EqMBYPQNIBF2pVoj80aBXY/p1g9+4jiIzYyHHGYIpZROpv3RT06PWMLlgg3+eCWbtaE=
-----END RSA PRIVATE KEY-----

4) Save your keyfile as "defaultkey.txt" or some other relevant name.

5) Run puttygen (this is included in the PuTTY package and you can download it seperately if you have PuTTY only from here).

6) Select Conversions -> Import Key.  If you want - put in a Key "passphrase" to protect the private key.  Then click "Save private key" button and save it in your PuTTY key file folder.

7) Launch PuTTY and log into the server.  Note that if you running PuTTY standalone (not from Elastic Fox or some other application that sets the environment) you will need to tell PuTTY where your PPK file is located.  This is done from Connection -> SSH -> Auth -> Private key file for authentication.  Browse to the PPK file you just generated.  You can save your session so you don't have to go through this again.

8) When you login using SSH when you get the "login as:" prompt you want to login is as root.  Their is no password because SSH has taken care of the authentication.