"system connections" can not be set up using KNetworkManager

[hvoss]

Binary package hint: knetworkmanager

"system connections" (which establish a network connect before a user is logged in) can not be set up with KNetworkManager.

My computer is connected to my network via WLAN. The network is to be connected before any user logs in. I can setup such a "system connection" in Gnome (network-manager) or manually in the shell (creating a /etc/NetworkManager/system-connections/ file), but I can not setup such a connection via KNetworkManager. In KNetWorkManager there is a option "[ ] System connection", but it's grey and you can not activate this option.

To reproduce this bug:
Start Kubuntu, click on the "KNetworkManager" icon, select "Connect To Other Network...", select your WLAN and click on "Connect", try to activate "System connection".