Most distro's have the netconfig utility to configure network cards. Have you tried doing it that way ? I wouldn't rely on KDE to configure your NICS in my opinion. You can also configure your network cards by using these commands:
And of course loading the modules for you particular cards with:
man each of them for more information. I'm not saying configuring by KDE is bad, I'm just saying making yourself familiar with the command line is good, cause that one day you can't get into KDE and you need network connection, you'd really be stranded.