I noticed a strange behaviour in my PHPWCMS website. It was with the phpwcms_output_section funtionality in phpwcms (access snippets of html from content enclosed in <!--SNIP_START//--><html><!--SNIP_END//-->)
because it returned nothing.
This could be happen on other parts where templates had to render a huge amount of data. (Like in my case)
After hours of tracking back this issue I remember the same problem on another non phpwcms related project.
The solution is to set ini_set('pcre.backtrack_limit', 1000000); in config.inc.php to raise the limit.
read the Bugreport: http://code.google.com/p/phpwcms/issues/detail?id=291 for details.
My Webhost all-inkl.com updated it's phpversion on my server and that was the reason, why my website stopped working.
Would have tried to do so in .htaccess oder php.ini
Which Version of PHP ?
And the host updated to php 5.3.
any more detailed info if you google for this value