After the Upgrade from php 4.0.6 to php 4.2.1 our Application crashes (httpd segmentation fault)

We used the dgb Debugger (dd.cron.ru) to figure out where it happens:
Inside a function when trying to make a global variable available with the global statement (global $xyz;).

We were not able to reproduce that error inside a short script. It only occurs in our (complex) Application (with a lot of classes) and only under certain circumstances.

after that, we tried to get a backtrace (we followed the guide in http://bugs.php.net/bugs-generating-backtrace.php).
After compiling php with --enable-debug we were not able to reproduce the error. Instead we got a lot of messages in 
the httpd-error_log:
-------------------------
zend_language_scanner.c(4363) :  Freeing 0x0825CDC4 (1 bytes), script=/usr/local/httpd/htdocs/AdditorDev/Website/page.php
Last leak repeated 1 time
./zend_execute.c(1999) :  Freeing 0x081EF674 (12 bytes), script=/usr/local/httpd/htdocs/AdditorDev/Website/page.php
Last leak repeated 3 times
./zend_execute.c(2002) :  Freeing 0x081EF454 (25 bytes), script=/usr/local/httpd/htdocs/AdditorDev/Website/page.php
zend_variables.c(106) : Actual location (location was relayed)
Last leak repeated 1 time
zend_hash.c(260) :  Freeing 0x08493A7C (48 bytes), script=/usr/local/httpd/htdocs/AdditorDev/Website/Additor/XmlConnect.php                   
Last leak repeated 597 times
--------------------------
I don't know what this means.

Our configure-line: 

./configure --enable-sockets --enable-memory-limit --with-mysql --with-apxs --with-xslt-sablot --with-sablot=/usr/local/lib --with-expat=/usr/local/lib --with-ldap --with-debugger --with-ftp --with-config-file-path=/etc/ --enable-trans-sid --enable-track-vars --enable-trans-sid --with-zlib-dir=/usr/lib --with-ming --with-oci8=/opt/oracle/OraHome1 --enable-xslt -enable-debug

thanx

Dirk Schmidt