This script:

<?php
function list_array ($array) {
   while (list ($key, $value) = each ($array)) {
      $str .= "<b>$key:</b> $value<br>\n";
   }
   return $str;
}

echo "$HTTP_USER_AGENT<hr>\n";
$browser = get_browser();
echo list_array ((array) $browser);
?>

Causes this:
[Mon Apr  3 15:08:48 2000] [notice] child pid 19324 exit signal Illegal instruction (4)
to be logged to the Apache 1.3.12 error_log file and nothing to be output to the browser (i.e. I get a dialog saying that the document contains no data).

I'm using PHP as an Apache DSO and my PHP configure line was:
./configure \
 --with-apxs=/w1/local/apache_1.3.12/sbin/apxs \
 --with-config-file-path=/w1/local/php/lib \
 --with-exec-dir=/w1/local/php/bin \
 --with-mysql=/w1/local/mysql \
 --with-oracle=/a9/oracle1 \
 --enable-debug=no \
 --enable-safe-mode=yes \
 --enable-track-vars=yes \
 --enable-short-tags=no

phpinfo() is showing under the Configuration heading:
Directive: browscap
Master Value: /w1/local/php/lib/browscap.ini
Local Value: /w1/local/php/lib/browscap.ini

I was having the exact same problem under PHP 3.0.12/Apache 1.3.9 several months ago and thought I would give it another try after recently upgrading.  I've also tried using browscap.ini files from various sources, the last being http://www.asptracker.com/.