PHP session expiring too early?

I am experiencing a strange bug after upgrading to PHP 5.2.4 with the Zend Optimizer 3.3.3. In two of our locally-hosted web applications, NolaPro and SugarCRM, the login sessions are expiring after 5 minutes of inactivity and I cannot figure why. The relevant values from my /etc/php.ini file are as follows: session.save_path = /var/lib/php session.use_cookies = 1 session.cookie_lifetime = 0 session.auto_start = 0 session.cookie_path = / session.cookie_domain = session.gc_maxlifetime = 1440 session.cache_limiter = nocache session.cache_expire = 180 /var/lib/php is set to 777 permissions. There is a cron job in /etc/cron.d/php: 09,39 * * * * root [ -d /var/lib/php ] && find /var/lib/php/ -type f -mmin +$(/usr/lib64/php/maxlifetime) -print0 | xargs -r -0 rm The script /usr/lib64/php/maxlifetime outputs the value "24" which is consistent with the value in the php.ini file. There are no .htaccess files in the root directories for either of the applications. Does anyone know what else could be causing this problem?