3.6.9 clients can't connect to the 3.6.10 server, it's impossible. First off they use different config files, and secondly the server protocol is entirely different so they have no idea how to talk to each other even if the config was the same. A mislabeled 3.6.10 build, which reports itself as 3.6.9 for some reason, will obviously be able to connect though. Real 3.6.9 builds can't, unless someone back-ported the new FS2NetD code, in which case those builds would not be supported by us.
I'm not sure what all of the current builds are though, as I have been busy with other stuff for a few weeks, so I really can't comment on the state of things or recommend any particular builds.