Messages SSL Error

Trying to connect to a Jabber service in Mavericks. Same server & config worked just fine in Snow Leopard, Lion and Mountain Lion.

Configuration is:

Server: chat.dco.dod.mil

Port: 5222

Use SSL: (unchecked)

I get an error that:

"Messages can't verify the identity of "chat.dco.dod.mil".

An SSL error has occured and a secure connection to the server cannot be made"

It presents the option to 'Always trust "chat.dco.dod.mil" when connecting to "chat.dco.dod.mil".' However, the server cert, the intermediate cert and the root cert are all already valid so I shouldn't have to. Nevertheless, if I check the box to tell it to trust, it still fails with the same message.

Corresponding Console log:

11/18/13 4:43:17.975 PM imagent[222]: CFNetwork SSLHandshake failed (-9820)

11/18/13 4:43:17.975 PM imagent[222]: [Warning] SocketStream: error Error Domain=NSOSStatusErrorDomain Code=-9820 "The operation couldn’t be completed. (OSStatus error -9820.)" occurred on input stream

Things I have tried:

- manually approving certs (same behavior)

- selecting "Automatically find server and port" in config (same behavior)

- selecting "Use SSL" with port 5223 (just hangs, no Console entries)

- selecting "Use SSL" with port 5222 (immediately disconnects with same Console log as above)