Fresh Installation of WP 3.5.1 fails to install themes or plugins

I downloaded WP 3.5.1 and installed. After completing the installation, I was unable to install plugins or themes. Any installation of a plugin or theme would fail with an error message about “unable to locate wp-content”.

I compared a pre-existing installation that had been upgraded to WP 3.5.1 instead of freshly installed for the distribution .zip.

There is a missing line in wp-content\index.php:

Broken:

<?php
// Silence is golden.

Fixed:

<?php
// Silence is golden.
?>
Hope this helps someone.