We have the "number of authentication failures" threshold set very low on our lab-managed Linux workstations and servers, including "attu", in order to combat brute-force password-guessing attacks.

If you have too many keys in your SSH key file on a CSE Linux host, and attempt to connect to that host, SSH will try each of the keys in your key file (if you don't specify any other directive, such as using a specific key). If the number of attempts exceeds our threshold, you'll see an error message similar to this one:

Received disconnect from 2: Too many authentication failures for username

This article - http://superuser.com/questions/187779/too-many-authentication-failures-for-username - has some useful information on the issue and its resolution.

The suggestion to log in with "ssh -o PubkeyAuthentication=no hostname" would let you log in so you can clean up your SSH keys.