For some reason, I've been running into a whole lot of "Error 500" related to /wp-includes/admin-ajax.php during the past couple of days, to the point that even my dashboard widgets (incoming links & plugins) are throwing the errors now.
Here's what I've tried:
* Disable all plugins - no luck.
* Change theme - no luck.
* Remove the entire /wp-admin and /wp-includes directories and reupload them from stock install - no luck.
* Replace stock jquery with Google Ajax Libraries API CDN.
My webhost doesn't offer too detailed logs about stuff like this, so all I can see is that there's an error 500, not what's causing it. My console in Chrome tells me, for example:
GET http://www.csicon.org/wp-admin/admin-ajax.php?action=dashboard-widgets&widget=dashboard_plugins 500 (Internal Server Error) jquery.js:2
(anonymous function) dashboard.js:1
Any thoughts or ideas?