[dokuwiki] Timeout when editing a page

Hello.

We use DokuWiki on our internal network, with Apache mod_auth_kerb for
authentication and kerbsso
(http://www.dokuwiki.org/install:apache_with_kerberos_sso) for
Single-Sign on in DokuWiki. Our clients are Windows XP with Internet
Explorer 6.

We have problems with timeouts, after roughly 30 minutes of editing a
page, a logon popup is displayed. If you do not enter the correct
username and password, a page with this text is displayed (and all
changes are lost):

============

Authorization Required

This server could not verify that you are authorized to access the
document requested. Either you supplied the wrong credentials (e.g., bad
password), or your browser doesn't understand how to supply the
credentials required.

------------------------------------------------------------------------
--------

Apache/2.0.52 (Red Hat) mod_perl/1.99_16 Perl/v5.8.5
mod_auth_kerb/5.0-rc4 PHP/4.3.9 mod_python/3.1.3 Python/2.3.4
mod_ssl/2.0.52 OpenSSL/0.9.7a Server at <servername> Port 80

============

At the same time, this is logged in Apache's error_log:

[Thu Nov 27 12:21:15 2008] [error] [client <IP address>]
gss_accept_sec_context() failed: A token was invalid (Token header is m
alformed or corrupt), referer:
http://<wikiserver>/<the_page_that_was_edited>

It doesn't look like it is a problem with DokuWiki (still, I have tried
changing settings in DokuWiki, "auth_security_timeout" to 10 hours,
"locktime" to two hours, no improvement). 

We have checked Kerberos config, the tickets have a 10 hour lifetime and
are nowhere near timing out when the logon popup is displayed.

We have changed session.gc_maxlifetime = 1440 in php.ini to 14400, no
improvement (may have been old open sessions, not sure when it is
applied).

I'm not that familiar with Apache, the "TimeOut" parameter doesn't seem
to apply (I may be wrong). Does anyone have an idea? The timeout seems
to be around 30 minutes, but that is an estimation and could be +/- a
number of minutes.

BR,
Daniel Lindgren

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