■

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
b3:c4:c8:a6:7c:5e:a4:bc:86:fa:b9:7c:f6:49:be:8d.
Please contact your system administrator.
Add correct host key in /home1/hatano/.ssh/known_hosts to get rid of this message.
Offending key in /home1/hatano/.ssh/known_hosts:5
RSA host key for nitamo.ddo.jp has changed and you have requested strict checking.
Host key verification failed.

orz

追記
SSHクライアント側のknown_hostから該当する行を削除すればよかっただけらしい。