I just upgraded to 4.5.3 today, but everything is working fine. I’m able to access the editor on Pages, Posts, etc. Are you sure you disabled all of your plugins?
The Child Theme itself (epik) doesn’t affect the editor since there isn’t any code within the theme that would cause any issues to your Admin.
Are you running the latest version of Genesis? There was an update for that recently as well.
I’ve never had that happen before, so I’m unsure what it could be. I’ve updated a lot of sites today and haven’t ran into any issues.
If you want to create a temporary user/password, I can login and see if I can quickly find out what the issue may be.