Either the administrator of the remote host computer has changed the host identification, or The ssh protocol has been upgraded from SSH1 to SSH2, or SOMEONE COULD BE EAVESDROPPING ON YOU RIGHT NOW (man-in-the-middle attack). It is NOT RECOMMENDED to connect to the remote host computer until you have contacted the system administrator and found out why the host identification has changed. The fingerprint of the host public key is "XXXXXXXXXXXXXXXXX"...