Found an issue with the Display Component option and JomSocial.
When you have Display Component to OFF, you cannot load the JomSocial main page as that view is also called "frontpage".
It looks like the gantry code in (/components/com_gantry/html/layouts/body_mainbody.php) is simply looking for "view=frontpage" and not actually checking to see if the page is the default menu item.
I solved my problem on this particular site by modifying line 37 from: $display_component = !($gantry->get("component-enabled",true)==false & JRequest::getVar('view') == 'frontpage');
and changed it to check if the component was com_content: $display_component = !($gantry->get("component-enabled",true)==false && (JRequest::getVar('option') == 'com_content' && JRequest::getVar('view') == 'frontpage'));
I would suggest that the conditional be changed to actually check to see if the page is the default menu item as I believe that was the intended purpose of this feature.
Have to say that I am LOVING Gantry though. It's a pleasure to develop with.
Thanks Rockettheme!