Trouble Updating Plugins through MPMU Dashboard Dev

I am attempting to update a few WPMU plugins and it is bringing me to a page not found page. The plugin I had tried this on was the login re-direct plugin, but it seems to be the same issue for all plugins. The install/update link links to: http://arcarugby.com/wp-admin/admin.php?page=wpmudev-updates but this page resolves to: http://arcarugby.com/not_found

I do have an out of date version of WPMU DEV Dashboard, however, when I attempt to update this, it gives me the error in the attached screenshot. Please let me know if you see anything obviously wrong with my approach to updating these plugins, or if you need any more information.

Thank you very much for the help.