[horde] Language doesn't stick after login

[Kristian Lance]

I three computers running Horde Groupware with Webmail--two w/latest 
Gentoo and one w/latest Fedora Core.

I originally thought I was lacking the correct locale support on these 
machines when I would select "French," log in, and the names of the 
Horde apps were in French, but everything else was in English.  Then, 
while trying to troubleshoot the problem, I set the default language in 
nls.php to "fr_FR."  This resulted in everything being translated to 
French properly, except that the login page was always in French, and 
even if I selected English on login, everything was displayed in French 
anyway.  So I set the default language in nls.php back to "" (blank), 
and continued testing.

Yesterday I had a look at the HTML source of the login page, and noticed 
that the form's language selection is called "new_lang," and that this 
value appears in the URL of the login page when another language is 
selected from the drop list on the login form.  So I logged into Horde 
again, and once I was logged in I added ?new_lang=fr_FR to the URL and 
bingo!  From that point onward I saw everything in French.

This exact behavior is reproduced on all three computers, all of which 
are running the latest versions of Gentoo/Fedora, PHP and Apache 2 (the 
db backend is PostgreSQL.  We have an older server that runs a version 
of Gentoo from a couple of years ago, as well as Apache 1.3x and PHP 
4.3x, and it handles Horde as expected--displaying the correct language 
when selected, without having to muck around.  I'm wondering if this is 
an Apache issue--some default changed in 2.0 for security reasons, or a 
change to how it handles sessions.  Horde's session name set for 
PHPSESSID, which matches the value in php.ini.

Can anyone give me some pointers, or suggest other tests that would 
reveal the cause of this problem?

Thanks!