Can't Edit / Save Posts or Pages Since 3.5.2 Upgrade

Hi,

I recently upgraded one of my WordPress sites to 3.5.2, but since then, I’ve not been able to save or edit any posts.

When using the text editor, I can type the content in, but when I hit “update” nothing is saved and it reverts back to the previous text. I tried creating a new page and the same thing happens—it just leaves the content part blank.

Anyone know why this might be happening and how to fix it?

Here’s what I’ve already tried.

– Repairing the WordPress database in phpmyadmin
– Adding this code to a htaccess file in the wp-admin folder:

<IfModule mod_security.c>
SecFilterInheritance Off
</IfModule>

– Updating the permalinks
– Testing another site to confirm that this issue was localized to just one domain, not the entire site.
– All plugins are disabled.

Thanks for the help!