Comment 5 for bug 390364

Whilst this is a known problem, that vinagre doesn't support the undocumented authentication types used by ARD server by default, a suitable current workaround seems to be to enable the "VNC viewers may control screen with password" option in system preferences. After doing this auth type 2 becomes available and vinagre can successfully connect using the given password.

I have asked upstream if they can do anything to better feed this information back to the user on failed connection.