Class 'Doctrine_Core' not found

[hjaffer2001]

Orange HRM works fine for me in my server except Performance Menu (which consist of KPI List and so on..)
Why this is so.. I am using
OrangeHRM ver 2.6.1, Apache 2.2, PHP 5.3.4.

Please Advice me.
Getting the below error:
Fatal error: Class 'Doctrine_Core' not found in /home/enduser/hrm/symfony/lib/vendor/symfony/lib/plugins/sfDoctrinePlugin/lib/database/sfDoctrineDatabase.class.php on line 81.

Thanks -
Haan