After upgrading from 3.6.1 to 3.8.1 I am no longer able to access update-core.php, themes.php, and plugins.php. The only message I get is the "Not Found" I have tried everything from disabling all plugins and changing the theme back to default via cPanel. I also tried a manual instal of 3.8.1 using a FTP client. Still no luck. Does anyone have a solution for this? Thank you for your time.
-Brian