Comment 7 for bug 1172752

Veli-Matti, can you try the fix in lp:~robert-ancell/lightdm/signal-fix and see if that works for you?

I can reproduce the problem if you get a greeter to start authentication twice in a row - in this case it seems likely that the first session child is signalled before the exec occurs and this causes the daemon to quit. In a real life case this might be possible to trigger by rapidly switching between users in a greeter (e.g. holding the up/down keys in Unity greeter).