app-admin/eselect is missing a slot dependency on sys-libs/ncurses, so since the creation of the slot for binary packages that need libncurses.so.5, portage will attempt to pull in that slot, since it's got the best visible version in it.
Thanks, fixed for eselect-1.4.6 and eselect-9999. Can't fix for 1.4.5 which is at EAPI 4 still.