Kfm file browser cannot access applications. In KDE desktop left click on a html or text file. Then do open with -> Browser -> Applications and the message: This group is empty! appears. This may be due to a misplaced directory. Important: This was not the KDE desktop that came with Red Hat 6.0 but is an installation of the KDE 1.1.2 version using foo.i386.rpm files from the stable tree at KDE's site.
Can't reprocude it here using the current Red Hat Linux release. I'd guess you're running in trouble with the fact that the RPMs from KDE's site install to /opt/kde instead of /usr, and your config files still point to /usr because you had the Red Hat RPMs first.