I've just created a new FB application and added the JFBC Invite module to my site. FB login is working fine, but under the Invite module, I'm getting:
serverfbml 'action' attribute must be within the application's connect url
I've confirmed that both the Invitee Welcome URL and Inviter Thank You URL are within the site as I specified it in the FB app. I've even tried setting them to the exact same front-page URL specified in the FB app.
My site is poetry.keenville.com. The JFBC Invite module is at the bottom of the right column on the JomSocial page.
I'm still seeing the error when I use my own Facebook account, but I have now created a test account on Facebook and I don't see the error when logged in to it. I don't know what's different about my Facebook account, but I don't think this problem is happening to anyone else, so I won't worry about it.
Now that I'm able to test properly, I've run into another issue with the Invite module. After the invitation steps are complete, I'm redirected to a Facebook page containing only the invite widget and nothing else. (The URL starts with 'www.facebook.com/plugins/serverfbml.php?api_key='.) Have you ever seen that before?
You have a typo in one of the URLs you've set in the parameters, and that's causing Facebook to choke. Check your parameters in the JFBCInvite module, and in one of the fields, you'll see:
http://poetry.keeville.com
You'll notice that an 'n' is missing. Fix that, and you should be good to go!
Hope that helps, but if not, as always, let us know!
Alex