I just upgraded to WP 2.84. I use the More Fields plugin, latest version 1.3, to add a couple of WYSIWYG boxes to my Pages admin. The frontend still works fine, all content is displayed correctly, but in the Pages admin the icons from the WYSIWYG boxes are now missing, and (in the ones that have content) content is displayed as html code, not in visual form.
The More Fields admin (in Settings) also looked fine, everything unchanged. To test further, I tried to create a new box. That worked until I tried to add a new field to the box - upon saving the new field, I got a "Fatal error: Call to undefined method more_fields_object::rewrite_rules() in /[server]/wp-content/plugins/more-fields/more-fields-manage-boxes.php on line 150"
I looked and that is this line:
Any help would be much appreciated.