BuddyPress Fatal Error When Creating New Site

More issues with BuddyPress. I have BuddyPress 1.6.2 installed with the Membership Beta version.

I had to revert back to 1.6.2 because 1.6.4 caused some of my pages to be inaccessible.

I just tried to create a new site and when I try to visit the site I get this error:

Fatal error: Class ‘BP_Group_Extension’ not found in /home/sisterh0/public_html/wp-content/plugins/bp-group-calendar/groupcalendar/bp-group-calendar.php on line 103

Again, please help.

Thanks so much,