Comment 4 for bug 1066410

Exactly same happens to me. Sometimes the lightdm able to load properly, but 90% persent of boots it goes black terminal screen weth mouse cursor. In roder to resolve this I going to terminal (alt+f1) and 'sudo restart lightdm'. Only then the login screen apears.

I've Dell XPS 14 Ultrabook (l421x) with Nvidia 630M (Optimus) and Intel HD4000. No nvidia proprietary drivers used and nouveau drivers are blacklisted. So only Intel is in use. btw when it works I've no other issues. (except of Nvidia optimus of course, but hit is a different issue).