Comment 7 for bug 1043513

Booting freshly installed quantal beta1 amd64 desktop under kvm (20120903.4)
As soon as I login, it kicks me back out to the graphical login. This was seen on the boot right after installation. If I manually reboot the system after that (i.e. shutdown kvm, properly start it back up without the -cdrom image specified), I am able to login.