This is getting old.

I hear they are going to include wicd soon, and it will not be too soon for me. The plasma-widget-network-manager fails as often as not. You can try System Settings-> Network Setting -> Network Management. Chances are good it will still fail. If you can get wicd installed it will work. If your network were up
sudo aptitude install wicd
would solve this problem. If it is on a CD you may be able to install it fom there, otherwise download the package on another computer, and install it with
sudo dpkg -i wicd_1.5.9-2_all.deb