What version of SL KDE are you using? Have you fully updated your Entropy database and upgraded all packages? KNetworkManager is history. The KDE GUI front-end to NetworkManager was replaced by kde-misc/networkmanagement
many months ago.
KNetworkManager used to be the KDE front-end to the DE-agnostic NetworkManager but the KDE front-end for NetworkManager is now the Plasmoid kde-misc/networkmanagement.
If you have updated the Entropy database and upgraded all packages you should not have the package knetworkmanager on your machine any more. After updating and upgrading, if knetworkmanager is still installed for some odd reason then uninstall knetworkmanager and install networkmanagement instead.