6
Hello everybody, thank you for all your answers and time.
I've just read your answers, and it was useful. @Mazar, the table was empty, but I cleared it anyway. The problem still was there.
@Mboyden, yeah, trying ROOTURL/user.php?op=logout allowed me to log out, and log in again later and work on it (that was another problem I had), but after a while the problem was again there...
@kris_fr, the test of Firefox at my job showed PASS in all the entries.
Anyway, looking up a bit more in google, I read that changing the value of var $enableRegenerateId from false to true in the line 65 of the file kernel/session.php all would work fine again, so I did it and it looks that everything is working OK at my job. The question is: Could someone explain why?