[limesurvey-developers] Problem with CSRF token

[Rudolf Naujack]

Hello,

we have an active survey with limesurvey 2.05 and some participants are
getting the message

The CSRF token could not be verified.
The request could not be understood by the server due to malformed
syntax. Please do not repeat the request without modifications.
If you think this is a server error, please contact the webmaster.

while most other participants have not problems with the survey.
Setting max_input_vars = 50000 in php.ini doesn't fix the problem. Also
setting a fix cookie domain in config.php doesn't help:

// Set the domain for cookie
'session' => array (
'cookieParams' => array(
'domain' => '.quotas.de',
),
),
// Set the cookie domain name for Csrf protection
'request' => array(
'csrfCookie' => array( 'domain' => '.quotas.de' ),
'enableCsrfValidation'=>false,
),

We are using
centos 6.4
with
php 5.3.3
apache httpd 2.2.15
mysql 5.1.69

Has anyone a solution / workaround for this problem?

Thanks
Rudolf Naujack