sudo apt-get dist upgrade. Apparently everything went well except that when it was done, in the terminal said there was an error. I didn't mind about it and shut system down. When I turn computer on again, everything was "ok" and then the list of sessions was in front of me... I selected my session, gave my password, pressed enter and it took me back to the sessions list. With every session happens the same: I can't log in.
I don't know what to do. I tried to use a previous version (the one shown in the start) and happens the same. I really need to get this fix.