I filed a bug with all the info over at the GNOME bugzilla, but the devs there say they can't reproduce the problem. That makes it, I think, a distro issue. Please take a look at http://bugzilla.gnome.org/show_bug.cgi?id=314988
Got your system all set up? Follow: http://www.gentoo.org/doc/en/utf-8.xml , make sure you USE="nls unicode" and emerge the latest pango.
Everything else works perfectly, I've been using this bilingual box for more than a year now (and I have the nls and unicode USE flags in my make.conf). Also, I'm working with pango-1.10.0, which doesn't rely on these flags.
according to your bugreport this seems to be an upstream problem, we'll keep an eye on it.