scim-libs scripts gives the following error while both installing and
uninstalling (showing uninstall case here:

# rpm -e scim-libs
/usr/bin/update-gtk-immodules: line 27:
/etc/gtk-2.0/i386-redhat-linux-gnu/gtk.immodules: No such file or directory
error: %postun(scim-libs-1.4.4-9.4.fc5.i386) scriptlet failed, exit status 1

Apparently, the right directory is i686-redhat-linux-gnu not i386...:
$ rpm -qf /etc/gtk-2.0/i686-redhat-linux-gnu/
gtk2-2.8.19-2

The problem is update-gtk-immodules in scim-libs scripts is called with the
wrong argument

$ rpm -q --scripts scim-libs-1.4.4-9.4.fc5
postinstall scriptlet (using /bin/sh):
/sbin/ldconfig
/usr/bin/update-gtk-immodules i386-redhat-linux-gnu
postuninstall scriptlet (using /bin/sh):
/sbin/ldconfig
/usr/bin/update-gtk-immodules i386-redhat-linux-gnu

I found another package which contains those calls with the right triplet:
$ rpm -q --scripts gtk2-2.8.19-2
postinstall scriptlet (using /bin/sh):
/sbin/ldconfig
/usr/bin/update-gdk-pixbuf-loaders i686-redhat-linux-gnu
/usr/bin/update-gtk-immodules i686-redhat-linux-gnu
$ rpm -q --qf '%{name}.%{arch}\n' gtk2
gtk2.i386

Versions:
$ rpm -q scim-libs gtk2 fedora-release
scim-libs-1.4.4-9.4.fc5
gtk2-2.8.19-2
fedora-release-5-5

PS please note there is no scim-libs component in this bugzilla for FC5.