GDM: black screen, only cursor

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http://forums.fedoraforum.org – I'm running Fedora 18 x86_64 on a system with a Nvidia GeForce 8400 GS videocard and the proprietary driver (xorg-x11-drv-nvidia-304.64-3.fc18.x86_64). Sometimes, at startup, the Gnome Display Manager (GDM) login screen does not appear: the screen remains black and only the mouse cursor is visible; nothing else happens and I'm forced to reboot the system. This issue has been occurring since I installed the closed-source Nvidia driver. Strangely (only a coincidence, maybe?), the problem happens only at the first boot and, after rebooting, everything works fine. The following lines from (HowTos)