Erroro: "403 - You are not authorized to view this resource"

Hmm. Not sure immediately. When you say fan page, do you mean a page on Joomla or a fanpage on Facebook itself?

If it's a 403 on Joomla, that's usually caused by a user trying to visit a page that they aren't of the right level to see.. a menu item marked as special, for instance, when the user is only 'registered'. Additionally, this can be caused if you're redirecting the users on logout to a page they don't have access too, or if you have JFBConnect set to leave them on the same page, but the page they are logging out of is for Registered users only... when they logout, they become guests trying to access a 'registered' page.

Hope this triggers some ideas of what could be happening. If not, send me a URL of a page that you think might be a problem. If you can get more information from the users on what they were doing at the time, whether they were logged in or not, or what page they were trying to hit, that will help diagnose the problem.

Thanks

Glad we're helping you along, now let's see if I can give some sage advice for the current issue.

First, make sure on the JFBConnect Overview page that all the add-ons are the most recent version.
Next, make sure there's no warning message about the ordering of the User plugin under the "Required Extensions" block. If so, fix it (see page 2 of the configuration guide for instructions). This likely isn't the issue since it's working mostly, but good to check.
Then, if you know the user's email address, check to see if it's already in your system as a 'normal' Joomla user. If it's there, and he tries to register, Joomla may be blocking us from creating another account with that same email address. You may want to enable the "Automatically Link Users By Email" (or something like that) in the User Configuration section.

Hopefully, one of the above helps you on your way, but if not, again, let us know If there are more issues, let me know if you're using any of the profile plugins for integration with CB, JomSocial, etc.

Thanks, and good luck!

That's definitely strange. A couple more things:
1) Even though Joomla registration is disabled now, I'm assuming it was enabled at one point. If so, still make sure the user doesn't have an account.
2) Are you using any of the profile plugins? If so, can you see if any of the fields you're importing into (in that system) are marked as required. Mainly, if you have a field like "Bio", try and mark it as not required. The reason I say this is because (especially with CB), if the user's FB profile has that field empty (no bio) and we try to save it with a required field empty, it can cause issues. It's a shot
3) Send me a link to your page and we'll see if we can see anything that might jump out at us.

I don't know how easy it is to get the one user to test (and don't know if you're frustrating the hell out of them).. hopefully not, and sorry for the troubles.

Thanks, and keep us posted!

Oh yeah, if you've disabled the Registration with Joomla, enabling the "Automatically link users by email" setting shouldn't have any bad effects, and (if that's the cause), it should fix your problem.. so I'd recommend enabling that!