4.3. Document contains no data or premature end of script headers (especially on BSDI or FreeBSD).
This usually means that your HTTP server ran out of resources during the execution of the link program. It couldn't create more sockets, is unable to create a process, or can't open any more files.
This usually happens in frames catalogs, when Interchange is sending more than one page simultaneously. And even more especially on FreeBSD and BSDI, which are often distributed with the kernel parameters SOMAXCONN and CHILD_MAX set to levels unsuitable for serving the web.
Go to <http://www.deja.com> and try searching for MAXUSERS. This should give you plenty of pointers on how to set these parameters properly.