All posts from guests go into a moderation queue. When I try and approve a post I get the message:
[domain name] - Error
Security error occurred. Please press back, refresh the page, and try again.
Pressing back, refreshing the page and trying again is not working.
Since it just started within the last 24 hours I'm thinking it might be some kind of server problem but I don't have any email from the server alerting me to a problem. It's possible they have been doing some tweaking on things. I need to go in and check that.
(On the other hand this may be a simple problem and I just haven't figured it out yet)