sh: kde-config: not found

I finally updated to kde 4.2. Yes, I was a critic of kde 4, now I love it. It is fast attractive, and very usable. I had one major problem, some programs would not launch from the start menu, firefox, thunderbird, avant window manager, compiz, emerald, and etc... These applications would not start from krunner either. So, like any good linux user, I started them in the terminal. They would run but each would give the error:
sh: kde-config: not found
It took two days of searching to find a solution and here it is:
sudo cp /usr/bin/kde4-config /usr/bin/kde-config


Slightly better(?) solution

I had the same problem (Slackware 13.0 64-bit). Create a symbolic link rather than copy the app - that way if you update kde4 in future (and the kde4-config app is updated), the link will point to the updated version:

cd /usr/bin
ln -s kde4-config kde-config

(I was logged in as root while doing this, su root/sudo etc... if you need to).