marketpress ERROR

Tks for the team for all your amazing plugins and theme.

I'm trying a lot of them and i've got a trouble with marketpress.

This is the what is showed when i check out :
Warning: session_start() [function.session-start]: open(/var/lib/php5/sess_744767815eb25d45001d0c5f9bc3a3c7, O_RDWR) failed: No such file or directory (2) in /sites/be6230/wp-content/mu-plugins/marketpress.php on line 681

and

Warning: Unknown: open(/var/lib/php5

You can try it at
http://norbert.be6230.g1site.com/

Tks for your help