When I turn off apc.stat it causes a 500 internal server error. I checked the apache error_log and it's something about:

[Tue Jun 26 10:02:59 2012] [error] [client 127.0.0.1] PHP Warning:  require(): Filename cannot be empty in /var/www/site1/public/index.php on line 17
[Tue Jun 26 10:02:59 2012] [error] [client 127.0.0.1] PHP Fatal error:  require(): Failed opening required '' (include_path='.:/usr/share/pear:/usr/share/php') in /var/www/site1/public/index.php on line 17

I checked that line and here's what it contains:

require('./wp-blog-header.php');

I don't see anything wrong with it. Here's my current APC config:

APC version: 3.1.10 PHP Version: 5.4.4

How do I resolve this error when i disable apc.stat?