I had exactly the same problem as you, and after almost 4 hours figured out that I had JavaScript files configured to be able to execute PHP by using
AddType application/x-httpd-php .php .js
in a local .htaccess file. After I changed this to
AddType application/x-httpd-php .php.js
in the .htaccess file, the problem went away.
Hope this helps,
Allison
