Program Error (Server Error 500)

<h1>Program Error (Server Error 500)</h1>
                  <hr />
             <p>
              <em>
              More information about this error may be available in the 
              server error log and/or program error log. 
              </em>
             </p>
             <hr />
               <pre>Base class package &quot;DADA::MailingList::Subscribers::&quot; is empty.
    (Perhaps you need to 'use' the module which defines that package first.)
 at /DADA/MailingList/Subscribers.pm line 8
BEGIN failed--compilation aborted at /DADA/MailingList/Subscribers.pm line 8.
Compilation failed in require at /is/htdocs/17424/www.end-if.de/E/cgi-bin/dada/mail.cgi line 172.
BEGIN failed--compilation aborted at /is/htdocs/17424/www.end-if.de/E/cgi-bin/dada/mail.cgi line 172.
</pre>