Ubuntu 12.04 LTS. I can't choose boot options Grub menu

I recently installed Ubuntu 12.04 from a live cd. When the grub boot options menu comes up, it automatically counts down 10 seconds and boots normally, but I can't choose the available options because there is no response on the menu when I press the up/down arrows on my keyboard.

Another symptom during bootup (after grub menu disappears and before the Ubuntu login screen appears) is a randomly pixilated colors screen appears for a few seconds. I'm adding this symptom in case it may help you guys to determine my problem's fix.