Market Press Plugin Error

I have the Premium account. I am getting this error in my WP Cart. I have the latest WP 3.2 and using Gensis Framework.

Can you tell me what this error mean:

http://scentualbodysolutions.com/store/shopping-cart/

error messages:
Warning: session_start() [function.session-start]: open(/var/chroot/home/content/j/a/m/username/tmp/sess_0c99b363099083316c0eee91b331e798, O_RDWR) failed: No such file or directory (2) in /home/content/j/a/m/jamesloyd/html/wp-content/plugins/marketpress/marketpress.php on line 840