Forum redirecting to Facebook Login

[del Drago]

Hello,

I've got a serious problem, and no one can seem to help. This occurs sporadically (once every 2-3 days).

If a user who is not logged into a Facebook account visits my forum, they are redirected from the forum to a Facebook login page.

When this happens, the only way for me to fix this is to "Clear System Cache" from Maintenance in Admin CP.

Users who are already logged into their Facebook accounts don't face this problem at all. They are able to visit the forum without issue.

I'm running suite 4.1.12 PL 1, and am using xcache for caching. (Clearing xcache doesn't solve this problem, though. Only clearing the system cache makes it go away).

The address of the redirect page is:

https://www.facebook.com/login.php?api_key=117381948333563&skip_api_login=1&display=page&cancel_url=http%3A%2F%2Fmythicscribes.com%2Fforums%2F%3Ferror_reason%3Duser_denied%26error%3Daccess_denied%26error_description%3DThe%2Buser%2Bdenied%2Byour%2Brequest.%26state%3Dd133fb807c8cf9635edf4fcb23a7a3e4&fbconnect=1&next=https%3A%2F%2Fwww.facebook.com%2Fdialog%2Fpermissions.request%3F_path%3Dpermissions.request%26app_id%3D117381948333563%26redirect_uri%3Dhttp%253A%252F%252Fmythicscribes.com%252Fforums%252F%26display%3Dpage%26response_type%3Dcode%26state%3Dd133fb807c8cf9635edf4fcb23a7a3e4%26fbconnect%3D1%26from_login%3D1%26client_id%3D117381948333563&rcount=1

It looks as if there is an error message embedded within that URL:

3DThe%2Buser%2Bdenied%2Byour%2Brequest.

Can anyone here think of any possible factors that could make something like this happen? Any brainstorming would be helpful.

Could something have changed with the Facebook API since I set it up nearly two years ago? Would reconfiguring the Facebook settings make a difference?

If worse comes to worse, would disabling Facebook Connect solve this? But then what happens to all of the members who registered via Facebook connect, and don't have passwords?

Thank you for your help.

Any ideas as to what may be happening here?

--------------- Added [DATE]1336626261[/DATE] at [TIME]1336626261[/TIME] ---------------

UPDATE:

This happened again a few minutes ago, and I was able to do some further testing.

This time clearing the system cache didn't make it go away. The only thing that made it stop was when I (on a different computer) logged into a facebook account. Then (on all computers) the forum worked fine again.