I switched to GDM from Slim a little while back and I've since noticed that my LINGUAS variable has been set wrong. If GDM_LANG gets set then it overwrites LINGUAS with the contents of LANG. In my case, this is en_GB.UTF-8 but I want it to be "en en_GB" since the UTF-8 part makes no sense for LINGUAS. When using Portage, LINGUAS is effectively blank since it doesn't recognise en_GB.UTF-8. The overwriting happens in /etc/X11/gdm/Xsession and can easily be removed. In a way, this could be expected behaviour but it causes problems, not only because of the UTF-8 suffix but also because of a bug in GDM that causes GDM_LANG to always be set, even if you've only chosen the "System Default" language. See the given URL for the Debian bug report on this issue.
Why are you defining LINGUAS at all ? This should most likely only be defined in your make.conf or user profile since this variable is of no use to users not compiling.
Sorry, I didn't realise that. I'd put it in /etc/env.d/02locale with the others. Thanks.
