Ubuntu Login Screen Resolution is Off

Solution 1:

General hint for X: Ctrl-Alt-numpadplus and ctrl-alt-numpadminus will cycle forward and back through the resolutions your X server is configured for.

Solution 2:

The login screen is run by a program called GDM. GDM uses the first resolution listed in your Xorg.conf modeline. In /etc/X11/xorg.conf what does your 'Screen' section have for resolutions?

Mine, for instance has this:

Section "Screen"
       Identifier "Default Screen"
    Device "VMWare SVGA"
    Monitor "vmware"

    Subsection "Display"
      Depth       4
      Modes       "640x480"
      ViewPort    0 0
    EndSubSection

    SubSection "Display"
      Depth       8
      Modes       "1280x1024"
      ViewPort     0 0
    EndSubSection

... and so on. It lists 1280x1024 at different color depths, as that is the resolution I run. The default 640x480 is what my login/GDM display uses. Try checking that out, and see if moving/changing that around fixes it.