Frank,
When I read your post, I thought you meant the page what blank/white, not just missing some content. I just went to your site, and can see the issue now. If I go to the About menu link, I see all the modules, but not the main content area (the article). The same is true for JomSocial and every other page I visit. If I simply append ?template=atomic to the URL, the content begins to show. That indicates that your template is not being told to render the component. Can you check your template to make sure that the following line is in there somewhere (and if you understand how, make sure it's in a place that will be executed):
<jdoc:include type="component" />
That's what renders the component output to the page, and it really just seems that that line isn't functioning with your current template. There's nothing in JFBConnect before, or now, that should alter the component output like that, but if you wanted to you, you can disable the JFBConnect system, user, authentication and content plugins. If that, and the JFBC modules are disabled, then JFBConnect shouldn't be modifying anything on your site at that poing. That should be just as effective as uninstalling it, but you're free to try that as well (you won't loose your settings).
Hope that helps, but keep us posted on what you find,
Alex