I have a D7 site up and running and working fine. Today I logged in to update some content, but I saw that the admin pages just show the system messages about necessary module updates and that's it. I tried several pages and they all show the same, no content except for the message on top. I can see the site content, but whatever link I click within the admin pages will show the right URL but the same content as the attached image.
Just a few months ago I logged in and everything was okay. What could be causing this? Any help is appreciated.