There are new locales for Serbian in glibc, please update system-config-languages accordingly. Instead of sr_CS and sr_CS@Latn, we now have sr_RS.UTF-8 - Serbian sr_RS.UTF-8@latin - Serbian (Latin) (note the change Latn -> latin) See also bug #235709
I fixed it in system-config-language-1.2.2-1.fc8. Thanks a lot. :)