This is how I got it corrected(Hope will help you guys):
Use the following code in your index.php file
ini_set('error_reporting', E_ERROR);
register_shutdown_function("fatal_handler");
function fatal_handler() {
$error = error_get_last();
echo("<pre>");
print_r($error);
}
In my case it tolde me that error/503.php was unavailable.
3.The issue was with testimonial extension I used(http://www.magentocommerce.com/magento-connect/magebuzz-free-testimonial.html)