This may be a duplicate, but I have not found a solution as yet. When I boot the computer, only the bottom half of the login screen is displayed on the top portion of the computer screen. Dragging the mouse around the screen causes artifacts to be displayed. I am able to log in, but still only see the bottom half of the display shown on the top half of the screen.
Computer: Acer Asprie AO751 OS: Ubuntu 12.4 LTS Video: Intel system controller hub (schpoulson) graphics controller Video driver in use: GMA 500 Grub: "...i915.modeset=1 quiet splash acpi=force"
If I log in then logout and back in immediately, I will get the full screen display as I should. If I switch to tty Ctrl+Alt+F1, login and run
sudo restart lightdm I can switch back to the gui and will have the full screen display. I have the same issue using either the netbook display or external display.