You should always be ssh-ing into your hosts using the fully qualified domain name, rather than 'vm09'.
From cygwin on your prime client, run
ssh-keygen -Rvm07.nubav.thinkon.net
ssh-keygen -R vm08.nubav.thinkon.net
ssh-keygen -R vm09.nubav.thinkon.net
ssh-keygen -R vm10.nubav.thinkon.net
You can also just delete the file C:\cygwin\home\<your username>\.ssh\known_hosts
Then, test passwordless SSH again as I described above (using the fully qualified domain name) to make sure you don't have to enter a password to reach the remote host's command line. Answer 'yes' you want to continue connecting. Make sure the hosts file on your prime client includes the hosts' fully qualified domain name so it resolves to its IP address.