error when launching KDE apps

I've been playing with Slackware 11 on my desktop box, using KDE 3.5.4. Annoying little bug comes up when I try to launch any KDE app (including when X starts and the K Desktop and Panels load), no problem with any non KDE apps (GIMP, Opera, etc.).

Basicly I get this;
http://ltmnet.dnsalias.com/images/other/octerr.gif

Tried adding octet/stream to Konqueror file associations, and that fixed the problem for Konqueror. Add it globally in Control Centre hasn't solved the problem for other apps though.

Any ideas?