I installed Ubuntu on my Dell Laptop (Windows 7 64 bit) using the Windows Installer. Everything was fine. After booting I got the choice http://assets.ubuntu.com/sites/ubuntu/540/u/img/download/U2.2.2_07_medium.jpg
But when I hit "Ubuntu" nothing happens. The monitor is black and stuck. Not even a cursor appears.
I have no idea what to do now. (Windows still works.)