yum groupinstall KDE isn't working. Please change the group names in shorter form like before f.e. kde-desktop, gnome-desktop od KDE, GNOME. I believe there was some policy for naming schemes.
The policy about the naming schemes is that the group-ids can never change. Because doing so would lead to breakage in people's kickstart configs.
It's worth noting that yum accepts any language "name" for a group, so if we want "short" group aliases we _could_ add them as "weird" language codes (I think). Eg. <name xml:lang=".nick_en">KDE</name> ...this could also work for "id like" names.