Comment 12 for bug 759974

I just had the same problem as Pander (#11).

The problem here was another installed webapp (DaviCAL) which overrode include_path within its apache-config.

BTW: I found out by creating /var/lib/roundcube/phpinfo.php:

 <?php phpinfo() ?>

and then calling http://myserver/roundcube/phpinfo.php and checked include_path within core section