I realized, that i cannot add new contacts in Roundcube mail. It seems that the MySQL update script failed at some upgrade and therefore the SQL insert failed. If you stomble upon this, you can find information regarding the problem inside the Roundcube folder /logs. It may look like this:
root hostname:[..]roundcubemail/logs# tail errors
[01-Aug-2013 11:51:45 +0200]: DB Error: [1054] Unknown column 'words' in 'field list' in [..]roundcubemail/program/lib/Roundcube/rcube_db.php on line 416 (POST /?_task=mail&_action=addcontact?_task=&_action=)
[01-Aug-2013 11:52:21 +0200]: DB Error: [1054] Unknown column 'words' in 'field list' in [..]roundcubemail/program/lib/Roundcube/rcube_db.php on line 416 (POST /?_task=mail&_action=addcontact?_task=&_action=)
[01-Aug-2013 11:52:23 +0200]: DB Error: [1054] Unknown column 'words' in 'field list' in [..]roundcubemail/program/lib/Roundcube/rcube_db.php on line 416 (POST /?_task=mail&_action=addcontact?_task=&_action=)
[01-Aug-2013 11:52:27 +0200]: DB Error: [1054] Unknown column 'words' in 'field list' in [..]roundcubemail/program/lib/Roundcube/rcube_db.php on line 416 (POST /?_task=mail&_action=addcontact?_task=&_action=)
[01-Aug-2013 11:52:29 +0200]: DB Error: [1054] Unknown column 'words' in 'field list' in [..]roundcubemail/program/lib/Roundcube/rcube_db.php on line 416 (POST /?_task=mail&_action=addcontact?_task=&_action=)
[01-Aug-2013 11:54:57 +0200]: DB Error: [1054] Unknown column 'words' in 'field list' in [..]roundcubemail/program/lib/Roundcube/rcube_db.php on line 416 (POST /?_task=mail&_action=addcontact?_task=&_action=)
[01-Aug-2013 11:55:10 +0200]: DB Error: [1054] Unknown column 'words' in 'field list' in [..]roundcubemail/program/lib/Roundcube/rcube_db.php on line 416 (POST /?_task=mail&_action=addcontact?_task=&_action=)
[01-Aug-2013 12:00:50 +0200]: DB Error: [1054] Unknown column 'words' in 'field list' in [..]roundcubemail/program/lib/Roundcube/rcube_db.php on line 416 (POST /?_task=mail&_action=addcontact?_task=&_action=)
root hostname:[..]roundcubemail/logs#I found the solution in this post: http://lists.roundcube.net/pipermail/users/2011-October/008036.html
The scripts to upgrade are located in
mysql -p roundcubemail
ALTER TABLE `contacts` ADD `words` TEXT NULL AFTER `vcard`;
ALTER TABLE `contacts` CHANGE `vcard` `vcard` LONGTEXT /*!40101 CHARACTER SET utf8 */ NULL DEFAULT NULL;
ALTER TABLE `contactgroupmembers` ADD INDEX > `contactgroupmembers_contact_index` (`contact_id`);
TRUNCATE TABLE `messages`;
TRUNCATE TABLE `cache`;