Comment 12 for bug 776028

I see the same problem using two machines running trusty amd64. However, in my case the remote system was configured to prompt the user for confirmation to allow incoming VNC connections. You may want to ensure this is not the case.

The behaviour can be changed using "vino-preferences", and then restarting the session to make the change effective.

If you have SSH access to the remote user, you can connect using ssh -Y, and run vino-preferences remotely via X forwarding.