As the error says, this could mean that someone is intercepting your traffic, hoping to get you to enter your username & password do they can use it for themselves.
This will also happen if you have accessed two different computers using the same name or IP address - ssh is warning you that the host key returned by the host doesn't match one that is on file for the same host.
I get this error from putty if I am using a VPN connection and connecting to the same private IP on two different networks, for example...
If you can find an explanation for the error, open up /home/mylogin/.ssh/known_hosts and remove the entry for the host you're trying to reach (probably the 3rd entry, judging by your error message). You'll be prompted to accept the new fingerprint the next time you try to connect.