After booting to the GUI in 12.04, I attempt to move to the virtual terminal (or shell, or tty) via Ctrl-Alt-F1 (F1 - 6), and the screen remains blank. I'm tried all 6 tty instances and the results are the same. Ctrl-alt-F7 brings me back to the GUI without a problem. Any thoughts?
This is usually caused because the graphical text-mode resolution set at boot up is not compatible with your video card. The solution is to switch to true text-mode by configuring Grub appropriately: