If you had the original host key you could restore it and this would stop the error.
Or, you could turn off StrictHostKeyChecking in your sshd config file.
... Doing this, however, is an awful, awful idea.
If there is a way for you to just run ssh-keygen -R server.example.com on client machines, that would be the best way -- because turning off host key checking is like saying, "Hey. Attack me." I get wanting obscurity when things change, but security should be priority #1 over obscuring changes.
