Please provide short reproducing script.

I found that it does not happen in case of simple recursion, but It crashes on
this script (I tryed this on two our servers that runs php 4.0.1pl2):

/test: settings.inc
/test/test: test.php3

settings.inc:
<?

  include"../settings.inc";

  $SELF_PATH = "$HOME_PATH/jforum";
  $SELF_URL  = "$HOME_URL/jforum";

?>


test.php3:
<? include "../settings.inc"; ?>


Visiting /test/test/test.php3 leads to crash:
[Thu Aug 24 15:33:11 2000] [notice] child pid 1094 exit signal Segmentation fault (11)

Yes, infinite include loop leads to crash. Don't do it.
Use include_once.

but this could leak to DoS attack from php pages authors, there should be a
configurable limit of include depth or something like this.