i have several zabbix servers running. on my two latest installations exporting templates/hosts fails. the preview works fine, the actual export has 0 bytes.

http-error.log shows:
[Thu Jul 29 13:31:00 2010] [error] [client xxxxx] PHP Fatal error: require_once() [<a href='function.require'>function.require</a>]: Failed opening required 'include/classes/class.domdocument.php' (include_path='.:/usr/share/pear:/usr/share/php') in /var/www/html/zabbix/include/config.inc.php on line 62, referer: http://xxxxxx/zabbix/export.php?sid=e0ff5339e229baad

the gui files are absolutely identical between the working and non-working versions (md5sum checked) - just it seems the conditions leading to the require_once() are not met on the other (working) systems