Indeed, replacing the "Failsafe" sections has restored my login screen!
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Login Screen Resolution
https://bugs.launchpad.net/bugs/16472
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I just looked over my xorg.conf and saw something strange:
Section "Device"
Identifier "Failsafe Device"
Boardname "vesa"
Busid "PCI:2:0:0"
Driver "nvidia"
Screen 0
EndSection
Section "Monitor"
Identifier "Failsaf