All areas of wp-admin go to 404 - Page Not Found
I am using Wordpress version 4.0. I understand there is a WordPress update, but I can't seem to access my admin area. I can log into wp-admin and see the dashboard menu items, but when I click on Updates, I get a 404 - Page Not Found. Same issue on both my sites. The same is true for all areas on the dashboard - when I click on any menu in the dashboard, I receive a 404 - Page Not Found. What do I need to do to fix this? Thanks for any help.