[horde] Horde 3.0.4 not changing language when selected at login time

[Carl Wilhelm Soderstrom]

I have a horde v3.0.4 installation, which is set up to allow users to select
their preferred language at login time. However, no matter what language you
select from the login page it does not change the language from the default.
(i.e. all the links, menus, and icon labels are in English).

If you select the language in your Horde options and save it, then restart
your web browser (it doesn't always seem to require a restart of the
browser, but usually does), then it sets the language.

Should it automatically set itself up to allow language changes, if the
option is there at the login page? Why might it work to set language options
one way, but not the other? I don't remember having to do anything special
for my horde v2.2.8 installation, but that installation works just fine in
this regard.

Which configuration options might affect this? 

This is installed on Debian Linux, and installed from the Debian packages,
then configured through the web-based GUI interface.

https://<hostname>/test.php shows that most things are set up and
working (memory limit set to 64MB, but that's the only red item).

Troubleshooting suggestions would be welcome, I'd rather put the onus on
myself here. (I'm not a skilled PHP coder tho).

-- 
Carl Soderstrom
Systems Administrator
Real-Time Enterprises
www.real-time.com