Why would the Drupal installation be selectively not responding?

I don't know what has happened, we updated the Drupal installation, some of the modules and suddenly the installation stopped working properly. The site by itself looks normal and so does the admin login. But once you try to do other stuff, things simply don't work, the page is reloaded instead of what it was supposed to do:

When doing an admin configuration change, content creation, user management or anything similar the change does not apply and the page is simply reloaded, including when putting the site in maintenance mode.
When clicking in pagination links, the page is only reloaded, the content doesn't change.

I suspect that the problem is DB related, sadly I haven't been able to find anything in the forums or somewhere similar to get me in the right direction. The modules we installed in the site are:

Chaos Tools
Views
Flickr
CKEditor
IMCE
Variable

Solution

At the end the problem for this was that there where translation files in the web root directory present. I don't know why that was causing the problem, but I'm posting this for future reference to anyone who comes to the same problem.