Just in case I need this for future updates to Wordpress.
http://ardentdev.com/fix-for-wordpress-xmlrpc-500-internal-server-error/
One of my WordPress-based sites was not working when I tried to publish posts containing images from Windows Live Writer. I was getting a 500 Internal Server Error. I ran the new latest version of Web Platform Installer. I think there is a mismatch in the MySQl database with the old sites and the new site.
Fortunately the workaround is easy. Just run the following database query to change the data type on the post_parent column:
ALTER TABLE wp_posts CHANGE post_parent post_parent BIGINT;
