I don't know if this is a KDE4 issue, but when I need to run an application as root, this dialogue "Run as root" comes up to type the root password. Well suddenly today it did not allow me to type the password. The vertical text cursor line is there, but no asterisks appear when I type the password. When I rename .kde4 and restart the session it is fixed, but what configuration file is responsible for this? I don't want to loose all my settings and start all over again.

I found the solution myself. In the the file ~/.kde4/share/config/kdeglobals I found:

[Passwords]
EchoMode=NoEcho

After removing these lines I got back my asterisk feedback. I must have changed the configuration by accident.