Cron job: Failed opening

Hello,
I use Drupal 6.13 and it works fine. But I have a problem if I run the cron ob. Drupal plot the following message:

Fatal error: require_once(): Failed opening required 'modules/views/includes/admin.inc' (include_path='.:/usr/share/php5:/usr/share/php5/PEAR') in /data/htdocs/DRUPAL_cms/aktiv/modules/views/views_ui.module on line 169

The variable $path in views_ui.module is OK, but it is working only. If I set temporary the absolute path in $path (include /data/htdocs/DRUPAL_cms/aktiv/) but then I have the next error in a other module.

I suspect, I have a mistake in my vhost configuration, but all other functions in Drupal is working. (I think :-) )

This is my vhost file:

<VirtualHost *:80>
DocumentRoot /data/htdocs/DRUPAL_cms/aktiv
 ErrorLog /var/log/apache2/cms_aktiv_error_log
 CustomLog /var/log/apache2/cms_aktiv_access_log combined
 AccessFileName .htaccess
  <Directory "/data/htdocs/DRUPAL_cms/aktiv">
        AllowOverride All
        Options Indexes FollowSymLinks
        Order allow,deny
        Allow from all
  </Directory>
AddHandler cgi-script .cgi .pl
ScriptAlias /cgi-bin/ /data/cgi-bin/
  <Directory "/data/cgi-bin">
        AllowOverride None
        Options +ExecCGI -Includes
        Order allow,deny
        Allow from all
  </Directory>
</VirtualHost>

If I disable the View Module I get this error in the reports:

	include_once(): Failed opening 'modules/cck/theme/theme.inc' for inclusion (include_path='.:/usr/share/php5:/usr/share/php5/PEAR') in /data/htdocs/DRUPAL_cms/aktiv/includes/theme.inc in Zeile 288.

include_once(modules/cck/theme/theme.inc): failed to open stream: No such file or directory in /data/htdocs/DRUPAL_cms/aktiv/includes/theme.inc in Zeile 288.

Thanks !!!