The quickest way to work around that problem would be to disable the SCSocialFindUs module. That should at least get the site back up and running.
As for the issue, I'm not sure what would cause that, but I'd recommend checking if you have the JFBCSystem plugin enabled? JFBConnect requires that plugin to operate, though it shouldn't crash like that if not.
Beyond that, have you tested other features, like social network authentication with Facebook or other networks? Curious if there are other issues that may be related.
Thanks,
Alex