For me this happens everytime a script exits whithout any output, e.g. a Perl CGI that does nothing or a PHP script that crashes before sending headers. The following PHP code kills itself and so triggers the bug:
<?php posix_kill(posix_getpid(), 6); ?> -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]