You'll need to enable Error Reporting, just temporarily while you test, so we can get a better idea of where the problem is coming from. I did just look at the site listed in Autotune, and it doesn't seem like the JFBCSystem plugin is enabled at all. I'm assuming you disabled it right now, but if not, that's probably part of the problem as well.
Let us know what error you're getting. Beyond that, check if you have any Firewalls or other security extensions installed and try disabling them, again temporarily, to see if that helps the problem.
Thanks,
Alex