Language switching not working for anon users - Plone 3.3.1 LinguaPlone 2.4.jarn.1

Hi,

I have a Plone 3.3.1 site running LinguaPlone 2.4.jarn1  We have a  
i18n domain for our product (in addition to the "plone" domain).   
Language selection works great for logged in users, but is broken for  
non-authenticated users.

The site has 4 available languages and sometimes is stuck in it's  
default language (EN) and is sometimes stuck in its second language  
(FR).  Clicking the flags seems to generate the correct urls, but  
fails to change the language in the UI.

This problem is present if Zope is accessed directly and also if it's  
proxied through apache.  We have no caching running in this test  
instance.

I have the following options selected in portal_languages

[x] Allow combined language codes like de_DE or en_UK.
[x] Display flags for language selection.
[x] Use language codes in URL path for manual override.
[x] Use cookie for manual override.

How would I go about debugging this issue?

Thanks,
--
David Siedband
http://zentraal.com

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