Problem with vnc on KDE

I use a 12.1 KDE on my laptops connected in a local home wireless network.
On a netbook I use like a file server I enabled throught yast VNC and left yast to open the firewall port.
On a client laptop I use KRDC to vizualize the server.
But I view only a KDE login screen. And after I fill username and password the VNC server show a message the it closes the connection.
Should I set other options on my server or client machines?

I configured the server to open the 5900 port (VNC) and auto-started krfb.
Now it works well, like in every other distro.
But the standard VNC One-time method by Yast, didn’t work for me.