Startx fails - stuck at login

[bznm]

After a power outage, I reboot the computer.
However when I login and press enter, the screen turns black for a moment and then the login screen comes again.
If I press ctrl alt f1 and type 'startx' the screen turns completely black for a moment and then I see the console again, with no apparent error but "server terminated successfully". This is the xorg log:http://pastebin.com/Q9aLxBZz .
I've already tried to rm the .Xauthority file or sudoing startx but it doesn't work. How could I solve the problem? I urgently need to use the computer :/

[Bashing-om]

bznm; Hello;


We may have a problem:
/vmlinuz-3.19.0-30-generic
Belongs to a End_Of_life release - vivid .
What release are you running, and what is the DeskTop environment ( xfce4 ??) ?
Show:

hostnamectl status
lsb_release -a
ls /usr/share/xsessions

Have you got the liveDVD(USB) on hand in order to conduct a file system check ?

maybe Yes

could be not so yes