So you've finished installing Ubuntu 12.04 through VirtualBox and you see a screen like this:
After you've clicked 'Restart Now' and the machine restarts, you get shown this:
Surprise surprise, there's nothing in your tray, hitting
enter doesn't work so just hard-reset the machine. Upon resetting, you see this:
click ok again.
That will reset your machine into command line mode. Log in (using the username and password you've provided while installing), then run
sudo apt-get update; sudo apt-get upgrade -y;
IF THE LOGIN SCREEN DIDN'T SHOW UP, (sometimes, you click the
Exit to login console button but then you just get a black screen) then hit
f1 and you will see the login prompt for you to login. If even that doesn't work, try
f1. These are commands to show the command line interface.