when i try to open any session from lightdm on my session, nothing happen (just lightdm opens again quickly). to open any session, i use the invited mode or the root mode from the terminal. for exemple to open lubuntu session on the root mode, i write "X&export DISPLAY=:0;sudo startlubuntu" (i should write "startlubuntu" with "sudo"). even i will install again ubuntu, i posted this problem only because more than 4 friends have the same problem. so i copied some of the log'files from /var/log : http://ubuntuone.com/4NirbFLdVrqaYo2qtWKRg4 and some files (.Xdefaults, .xsession-errors, .xsession-errors.old) from my home folder: http://ubuntuone.com/10iKFxyIuNQfYKrcMhccRm
(this problem happened to me before updating to v.12.10 and my friends use simply ubuntu 12.04 without any modification)
