Buddypress theme pack error meassge

Hello: I just installed the buddypress theme pack and am getting this error meassge on the buddypress related pages such as groups or activity:

Warning: session_start() [function.session-start]: Cannot send session cache limiter – headers already sent (output started at /home/randit/public_html/dotbizsite.com/wp-content/themes/core/members/single/home.php:12) in /home/randit/public_html/dotbizsite.com/wp-content/themes/core/header.php on line 8.

I am not an IT person so any easy help is appreciated. The site is http://dotbizsite.com. Thank you.