error on upgrade page of pro sites

Hi

I'm getting the below error when I'm logged into my site, it doesn't appear when i'm logged out could you help please.

Warning: session_start() [function.session-start]: open(/tmp/sess_79814ff972d81755c13dd21b0039978b, O_RDWR) failed: Permission denied (13) in /home/goodeye/public_html/wp-content/plugins/pro-sites/pro-sites.php on line 679

Many thanks

Dave