I have a Joomla 2.5 site running on Debian Squeeze. I'm also new to server management.

I have an intermittent problem with the site crashing and only showing a blank white page. Sometimes it's good for a couple days before it happens, sometimes it happens within an hour. The site is still in development and not live, so there is very little traffic.

I continually get a PHP Fatal error. Here's what the PHP log says every time the site is loaded and the error occurs:

PHP Fatal error: Cannot call overloaded function for non-object in /path-to-site/public_html/libraries/rokcommon/include.php on line 25
PHP Fatal error: Class 'JFactory' not found in /path-to-site/public_html/libraries/joomla/session/storage/database.php on line 71

I made sure all the software is up to date, including Joomla and everything that uses rokcommon. I've reinstalled both the Joomla core and rokcommon and other extensions multiple times. I turned of all caching on the Joomla side, but do have APC installed on the server side. I've read everything I can find on the issue in Joomla forums, etc to no avail. I've seen some mentions that it can be caching related, which would make sense considering the intermittent nature.

Lines 23-25 of include.php are:

// Check to see if there is a requiments file and run it.
// Catch any exceptions and log them as errors.
$requirements_file = rokcommon_cleanPath(ROKCOMMON_LIB_PATH . '/requirements.php');

Lines 70-71 of database.php are:

// Get the database connection object and verify its connected.
$db = JFactory::getDbo();

Any help on a direction to go would be greatly appreciated. I'm new to this, but trying to learn.