Hmm....Not sure about RH9, but there's a workaround that's worked okay for me in a couple of other distros-
log in as root, open the KDE Control Center, go to KDE Components>File Manager>Previews. Uncheck "file" in the list, log in as your normal user, and try it again.
Hope this helps. BTW, as far as I know, it's a bug - found this workaround on a mailing list somewhere. Seems to have been cured in later versions of KDE. Does'nt happen in Slack 9.1, anyway.