For some reason this has happened a few times on our site and again today. (over the course of a few different wordpress versions) Something causes all the comment_status fields on all the posts (over 15000) in the database to switch to "closed". Similar issue to this one here but there was no solution: http://wordpress.org/support/topic/comments-disabled-on-posts?replies=8. Tried searching the forums and the web to no avail.
I'm very familiar with the WordPress discussion settings in the dashboard and know how to switch them all back to "open" in the database but this isn't good as we have posts/pages that need to have comments off.
I have searched through the source code of all the plugins I have in use and none of them have anything matching with "closed" or "comments_status" that would cause the status to switch on all the posts at once.
What could possibly be causing this and does anyone else have the issue?