using apache with php-module v4.0.6, mysql3.23.35; configure:
'./configure' '--with-apxs=/virtual/development/httpd/bin/apxs' '--without-debug' '--with-config-file-path=/virtual/development/httpd/conf' '--enable-sysvsem' '--enable-sysvshm' '--enable-shmop' '--with-ftp' '--enable-track-vars=yes' '--enable-gd-native-ttf' '--enable-memory-limit=yes' '--enable-magic-quotes=yes' '--enable-trans-sid=yes' '--enable-inline-optimization' '--with-mysql=/usr/local/mysql' '--with-ttf=/usr/lib/freetype2' '--with-zlib' '--enable-calendar' '--with-jpeg-dir=/usr/local/lib' '--with-pnglib=/usr/local/lib' '--with-gd' '--enable-sockets'


we had no problems at all with 4.0.5, but since we have 4.0.6 on our server, 
we get unmotivated "memory exhausting at any script on any line".
the error does not occure regularly, but when it happens, it comes many times in a row, just like php needs a bit of time to eat the memory, then crashes multiple times, and finally finds peace for a few hours working correctly. till the next day or so.
I can't give you a code-snippet to reproduce it, because when the error occurs, you can simply reload the page and most of the times it then works, but only most of the times...