When do I receive :Server does not support compatible authentication...?

Sometimes I’'m receiving this error:

Server does not support compatible authentication mechanism.:

at org.jivesoftware.smack.NonSASLAuthentication.authenticate(NonSASLAuthentication .java:80)

at org.jivesoftware.smack.XMPPConnection.login(XMPPConnection.java:345)

at com.skyrider.agent.identity.IdentityConnection.login(IdentityConnection.java:73 2)

at com.skyrider.agent.identity.IdentityDispatcher.login(IdentityDispatcher.java:11 66)

at com.skyrider.agent.identity.requests.LoginRequest.run(LoginRequest.java:29)

at com.skyrider.agent.identity.IdentityDispatcher.run(IdentityDispatcher.java:572)

It seems like this message was not eve sent. But been issued by the client side.

When does SMACK therow this exception? why?