Then the conclusion seems to be that the 2 different versions of OpenSSH can't talk to each other properly.
Can you establish other kinds of connections (ie ftp, http, etc)?
If you can't, this can indicate a failure for instance in the wiring.
In any case, you might want to consider upgrading to the latest version of OpenSSH.
There are quite some security holes patched since your versions were released:
http://www.openssh.com/security.html