I've found an issue where it seems that Gravity Forms is causing the Upload New Media action of the admin panel to fail.
When the plugin is active Trying to upload media through the media manger fails with the error.
Cannot redeclare create_initial_post_types() in /Users/stewartritchie/Dropbox/Sites/LLHP/wp-includes/post.php on line 19"
(Local dev environment)
From what I can tell it seems that something in Gravity Forms is telling PHP to include '/wp-includes/post.php' when it clearly has already been included, but I can't find it anywhere!
To make this slightly worse it appears to happen randomly, two or three uploads will go through fine then the error happens, after that all fail.
Gravity forms is currently the only plugin active.