Peter,
Can you tell me what the name of the step is? Basic Settings, Facebook App, or Site Check? Do you have to do anything for the error to show (like clicking the "Save Settings" button), or does it appear right when you reach the step?
Also, is this on a site that's run Autotune before, or is this a new site?
Not sure what that error would be from, but we'll gladly help narrow things down.
Thanks,
Alex