Looks like the guys from RH (or KDE.org? whoever created the RPMS...) screwed some things up. I had to reinstall RH8 today (HD-crash), and first thing I did was to download the RPMS from kde.org and installing them. Still I'm experiencing the same problems.
Looks like it's some kind of bug or incompatibility in the RH8 RPMS, because I'm experiencing the same problems. I also had problems with starting some apps. They always complained about a function, that libDCOP didn't find (don't know the name anymore, got it fixed by moving the old qt-library to another place and leaving only the qt-3.1.2). Perhaps it's related to the bug (if it is a bug...) in the control panel?