my problems started when I moved my website to another folder (from /dev/ to /). I have gone through the whole database in order to change all the hardcoded /dev/ into / but I still notice that wordpress, somehow, still uses the old values.
Basically the website uses information that are not there anymore. I checked my own and the server cache and they all seem to be clean (the server doesn't even seem to have that feature on).
So, I am pretty much lost...
FIXED: The problem was related to the revision number of every information. Having changed some values directly from the DB but not the revision number, wordpress would reject the change and show nothing (as there were no previous versions).
I just entered all the missing information by hand and it worked.
Basically, don't mess with the DB. Wordpress doesn't forgive!