This package is currently failing to build in devel because gnome-libs has been dropped from Core and hasn't made it into Extras yet. Bug #198245 is a review request for gnome-libs The proposed gnome-libs-devel package has a dependency on libSM-devel, so there should be no need for gtktalog to buildrequire libSM-devel for FC6.
I've simply dropped gtktalog for FC-6 entirely. There has been an effort started to get it updated to use gtk2 about one year ago, but it seems like it has gone nowhere. This is too bad. I really hope someone would step up to finish the work...