Comment 3 for bug 1312526

I suffer the same issue.
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Distributor ID: Ubuntu
Description: Ubuntu 14.04 LTS
Release: 14.04
Package: lightdm 1.10.1-0ubuntu1
Greeter: unity-greeter 14.04.10-0ubuntu1
Uname: Linux 3.13.0-24-generic i686
Architecture: i686
CurrentDesktop: Mate
AlternativeDesktop: Unity
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/etc/lightdm/lightdm.conf

[SeatDefaults]
user-session=true
greeter-session=unity-greeter
allow-guest = false
greeter-hide-users = true
greeter-show-manual-login = true
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/usr/share/xsessions/lightdm-xsession.desktop

Exec=mate-session
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/var/log/auth.log

lightdm: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "tester1"
lightdm: pam_unix(lightdm:auth): authentication failure; logname= uid=0 euid=0 tty=:0 ruser= rhost= user=tester1
lightdm: pam_winbind(lightdm:auth): getting password (0x00000388)
lightdm: pam_winbind(lightdm:auth): pam_get_item returned a password
lightdm: pam_winbind(lightdm:auth): user 'stoledo' granted access
<< and nothing more logged :-\ >>
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/var/log/lightdm/lightdm.log

[+71.88s] DEBUG: Session pid=4209: Continue authentication
[+71.90s] DEBUG: Session pid=4685: Got 1 message(s) from PAM
[+71.90s] DEBUG: Session pid=4209: Prompt greeter with 1 message(s)
[+76.41s] DEBUG: Session pid=4209: Continue authentication
[+76.73s] DEBUG: Session pid=4685: Authentication complete with return value 0: Success
[+76.73s] DEBUG: Session pid=4209: Authenticate result for user tester1: Success
[+76.73s] DEBUG: Session pid=4209: User tester1 authorized
[+76.73s] DEBUG: Session pid=4209: Greeter requests default session
[+76.73s] DEBUG: Seat: Failed to find session configuration true
[+76.73s] DEBUG: Seat: Can't find session 'true '
[+76.73s] DEBUG: Session pid=4209: Greeter start authentication
[+76.74s] DEBUG: Session pid=4735: Started with service 'lightdm', username '(null)'
[+76.74s] DEBUG: Session pid=4685: Exited with return value 0