Since I'm no fan of redhat-config-packages, and I prefer to do stuff with rpm from the commandline anyways, I've found a roundabout way of using config-packages to give me a list of 'to-install' packages, and then cut-n-paste into a script... rh-config-packages sorts out the dependencies, but I have other scripts that will do this... all I really want to have is the packages list of old. I installed the KDE 'bits' my way, now I need development packages on the system, and this will require a lot of time, just to get the list of pkgs installed under 'Development Tools' 'X Software Devel' etc.
I had similar issues with an upgrade. redhat-config-packages and up2date were both unreliable for me. I found yum to be much better than either and switched to it exclusively. The lack of a front end is a bit challenging, but among other things, I wrote a perl script to screen-scrape yum's repository and installed file lists and give me a nicely grouped listing of what's on the system.
A short description of the script is posted at http://www.dagolden.com/cgi-bin/main/index.cgi?page_id=YumGroupsScript
You can get the script itself at http://www.dagolden.com/files/scripts/yumgroups
No warranties, of course! YMMV.
Good luck,
David