I have just updated a site to from 3.7.1 to 3.8. Running on IIS7.5, about which I can do nothing, so "switch to Linux" isn't an answer I can use!
The auto-install failed, so I deleted wp-admin and wp-includes and maint, temporarily renamed the plugins folder, uploaded the WP files from the downloaded ZIP file, including the root files.
The site is in a sub-directory (wordpress) but intended to run from the root, so I made sure I still had the edited version of root/index.php including the directory:
require( dirname( __FILE__ ) . '/wordpress/wp-blog-header.php' );
and now I get a 500 error for the site and the backend. (There's no point in giving you the URL as I have temporarily reinstated a skeleton HTML site till I get this fixed.)
I still have the wp-config.php and web.config that were working before the update.
Before I try to get server logs from support, can anyone spot anything I have done obviously wrong please? This is the first time in about 50 updates that things have gone wrong, and I am floundering a bit :(