WP-Ecommerce Error: session_start()

Guys I’m using WP 3.0 with the plugin WP-Ecommerce 3.7.6.7 unfortunately is giving this error:

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/cattur/public_html/index.php:2) in /home/cattur/public_html/wp-content/plugins/wp-e-commerce/merchants/paypal_certified.php on line 788

Already have a good time researching about anything and think, some good samaritan help me please …